if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc() to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com --- drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO); + GFP_KERNEL); if (!ttm->pages) return -ENOMEM; + + memset(ttm->pages, 0, ttm->num_pages * sizeof(void *)); + return 0; }
@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address), - GFP_KERNEL | __GFP_ZERO); + GFP_KERNEL); if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address))); + ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address), - GFP_KERNEL | __GFP_ZERO); + GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM; + + memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address)); + return 0; }
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL);- memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
- return 0; }
@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL);if (!ttm->pages) return -ENOMEM;
memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; }
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL);- memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));
- return 0; }
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 5:00 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail. it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));return 0;@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0;}
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM;memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));return 0;
Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo,
bool zero_alloc)
static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO); + GFP_KERNEL); if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
return 0; }
@@ -108,10 +111,12 @@ static int
ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm)
ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address), - GFP_KERNEL | __GFP_ZERO); + GFP_KERNEL); if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) +
sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int
ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm)
{ ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->dma_address) return -ENOMEM;
+ memset(ttm->dma_address, 0, ttm->num_pages *
sizeof(*ttm->dma_address));
return 0; }
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source treehttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.18-rc3&id=a421ef303008b0ceee2cfc625c3246fa7654b0ca mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
________________________________ From: Koenig, Christian Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 6:53 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 5:00 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));return 0;@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0;}
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM;memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));return 0;
Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.18-rc3&id=a421ef303008b0ceee2cfc625c3246fa7654b0ca mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use
vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c
b/drivers/gpu/drm/ttm/ttm_tt.c
index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo,
bool zero_alloc)
static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
return 0; }
@@ -108,10 +111,12 @@ static int
ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm)
ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) +
sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int
ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm)
{ ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->dma_address) return -ENOMEM;
+ memset(ttm->dma_address, 0, ttm->num_pages *
sizeof(*ttm->dma_address));
return 0; }
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
________________________________ From: Christian König ckoenig.leichtzumerken@gmail.com Sent: Wednesday, April 20, 2022 7:55 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source treehttps://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7CKevinYang.Wang%40amd.com%7C2e9fd86a27d64a39432508da22c4b1f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860525454702938%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CiP9x3grwQ2aXFZPjpsAtwLCpBVeJufbGngy%2BtXLFbM%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 6:53 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 5:00 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));return 0;@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0;}
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM;memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));return 0;
Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is: 1) Change the test case to use something larger than 1TiB. 2) Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com *Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7CKevinYang.Wang%40amd.com%7C2e9fd86a27d64a39432508da22c4b1f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860525454702938%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CiP9x3grwQ2aXFZPjpsAtwLCpBVeJufbGngy%2BtXLFbM%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use
vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it
will
cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c
b/drivers/gpu/drm/ttm/ttm_tt.c
index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo,
bool zero_alloc)
static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
return 0; }
@@ -108,10 +111,12 @@ static int
ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm)
ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages)
- sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int
ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm)
{ ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->dma_address) return -ENOMEM;
+ memset(ttm->dma_address, 0, ttm->num_pages *
sizeof(*ttm->dma_address));
return 0; }
[AMD Official Use Only]
Hi Chris,
1) Change the test case to use something larger than 1TiB. sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right? the system availed memory about 2T, but it will still fail.
2) Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin ________________________________ From: Koenig, Christian Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 8:42 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is: 1) Change the test case to use something larger than 1TiB. 2) Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
________________________________ From: Christian König ckoenig.leichtzumerken@gmail.commailto:ckoenig.leichtzumerken@gmail.com Sent: Wednesday, April 20, 2022 7:55 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source treehttps://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7CKevinYang.Wang%40amd.com%7C2e9fd86a27d64a39432508da22c4b1f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860525454702938%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CiP9x3grwQ2aXFZPjpsAtwLCpBVeJufbGngy%2BtXLFbM%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 6:53 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 5:00 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));return 0;@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0;}
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM;memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));return 0;
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
- Change the test case to use something larger than 1TiB.
sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here.
Regards, Christian.
the system availed memory about 2T, but it will still fail.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 8:42 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is:
- Change the test case to use something larger than 1TiB.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com mailto:ckoenig.leichtzumerken@gmail.com *Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7CKevinYang.Wang%40amd.com%7C2e9fd86a27d64a39432508da22c4b1f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860525454702938%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CiP9x3grwQ2aXFZPjpsAtwLCpBVeJufbGngy%2BtXLFbM%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use
vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit,
it will
cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c
b/drivers/gpu/drm/ttm/ttm_tt.c
index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object
*bo, bool zero_alloc)
static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
return 0; }
@@ -108,10 +111,12 @@ static int
ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm)
ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages)
- sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int
ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm)
{ ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->dma_address) return -ENOMEM;
+ memset(ttm->dma_address, 0, ttm->num_pages *
sizeof(*ttm->dma_address));
return 0; }
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 8:56 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
1) Change the test case to use something larger than 1TiB. sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here.
Regards, Christian.
Kevin:
it is ok to explain why we do not need fix this issue at this stage.
thanks.
Best Regards, Kevin the system availed memory about 2T, but it will still fail.
2) Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin ________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 8:42 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.commailto:ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is: 1) Change the test case to use something larger than 1TiB. 2) Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
________________________________ From: Christian König ckoenig.leichtzumerken@gmail.commailto:ckoenig.leichtzumerken@gmail.com Sent: Wednesday, April 20, 2022 7:55 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source treehttps://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7CKevinYang.Wang%40amd.com%7C2e9fd86a27d64a39432508da22c4b1f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860525454702938%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CiP9x3grwQ2aXFZPjpsAtwLCpBVeJufbGngy%2BtXLFbM%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 6:53 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
________________________________ From: Koenig, Christian Christian.Koenig@amd.commailto:Christian.Koenig@amd.com Sent: Wednesday, April 20, 2022 5:00 PM To: Wang, Yang(Kevin) KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.orgmailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.orgmailto:amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit, it will cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.commailto:KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));return 0;@@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->pages) return -ENOMEM;memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address)));ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0;}
@@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
GFP_KERNEL | __GFP_ZERO);
GFP_KERNEL); if (!ttm->dma_address) return -ENOMEM;memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address));return 0;
On 4/20/2022 6:26 PM, Christian König wrote:
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
- Change the test case to use something larger than 1TiB.
sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here. >
AFAIU, for the purpose of ttm use, fallback to vmalloc is fine.
* Please note that any use of gfp flags outside of GFP_KERNEL is careful to not * fall back to vmalloc. *
Actually the current implementation documents the behavior, but it is deep inside the implementation to be noticeable - at least not obvious while using kvmalloc_array.
Thanks, Lijo
Regards, Christian.
the system availed memory about 2T, but it will still fail.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 8:42 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is:
- Change the test case to use something larger than 1TiB.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com mailto:ckoenig.leichtzumerken@gmail.com *Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fh%3Dv5.18-rc3%26id%3Da421ef303008b0ceee2cfc625c3246fa7654b0ca&data=05%7C01%7Clijo.lazar%40amd.com%7C908fad4b756248e06e5e08da22cd4463%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860562263637656%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=34hU%2FcxcRgBiiZ2jdNxTVmU7t4JF7TR27hx1b119U9g%3D&reserved=0 mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang:
if the __GFP_ZERO is set, the kvmalloc() can't fallback to use
vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
to allocate memory, when request size is exceeds kmalloc limit,
it will
cause allocate memory fail.
e.g: when ttm want to create a BO with 1TB size, it maybe fail.
Signed-off-by: Yang Wang KevinYang.Wang@amd.com
drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c
b/drivers/gpu/drm/ttm/ttm_tt.c
index 79c870a3bef8..9f2f3e576b8d 100644 --- a/drivers/gpu/drm/ttm/ttm_tt.c +++ b/drivers/gpu/drm/ttm/ttm_tt.c @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object
*bo, bool zero_alloc)
static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) { ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), - GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * sizeof(void *));
return 0; }
@@ -108,10 +111,12 @@ static int
ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm)
ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(*ttm->pages) + sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->pages) return -ENOMEM;
+ memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages)
- sizeof(*ttm->dma_address)));
ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); return 0; } @@ -120,9 +125,12 @@ static int
ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm)
{ ttm->dma_address = kvmalloc_array(ttm->num_pages, sizeof(*ttm->dma_address),
- GFP_KERNEL | __GFP_ZERO);
- GFP_KERNEL);
if (!ttm->dma_address) return -ENOMEM;
+ memset(ttm->dma_address, 0, ttm->num_pages *
sizeof(*ttm->dma_address));
return 0; }
On 2022-04-20 09:23, Lazar, Lijo wrote:
On 4/20/2022 6:26 PM, Christian König wrote:
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
- Change the test case to use something larger than 1TiB.
sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here. >
AFAIU, for the purpose of ttm use, fallback to vmalloc is fine.
* Please note that any use of gfp flags outside of GFP_KERNEL is careful to not * fall back to vmalloc. *
That's weird, because kvcalloc does the same thing. If that were not able to fall back to vmalloc, it would be pretty useless.
static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t flags) { return kvmalloc_array(n, size, flags | __GFP_ZERO); }
Maybe kvcalloc is the function we TTM should be using here anyway, instead of open-coding the kvmalloc_array call with an extra GFP flag.
Regards, Felix
Actually the current implementation documents the behavior, but it is deep inside the implementation to be noticeable - at least not obvious while using kvmalloc_array.
Thanks, Lijo
Regards, Christian.
the system availed memory about 2T, but it will still fail.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 8:42 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is:
- Change the test case to use something larger than 1TiB.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com mailto:ckoenig.leichtzumerken@gmail.com *Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h... mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang: > if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
> to allocate memory, when request size is exceeds kmalloc limit, it will > cause allocate memory fail. > > e.g: when ttm want to create a BO with 1TB size, it maybe fail. > > Signed-off-by: Yang Wang KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com > --- > drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c > index 79c870a3bef8..9f2f3e576b8d 100644 > --- a/drivers/gpu/drm/ttm/ttm_tt.c > +++ b/drivers/gpu/drm/ttm/ttm_tt.c > @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) > static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) > { > ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->pages) > return -ENOMEM; > + > + memset(ttm->pages, 0, ttm->num_pages * sizeof(void *)); > + > return 0; > } > > @@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) > ttm->pages = kvmalloc_array(ttm->num_pages, > sizeof(*ttm->pages) + > sizeof(*ttm->dma_address), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->pages) > return -ENOMEM; > > + memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address))); > + > ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); > return 0; > } > @@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) > { > ttm->dma_address = kvmalloc_array(ttm->num_pages, > sizeof(*ttm->dma_address), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->dma_address) > return -ENOMEM; > + > + memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address)); > + > return 0; > } >
[AMD Official Use Only]
________________________________ From: Kuehling, Felix Felix.Kuehling@amd.com Sent: Thursday, April 21, 2022 5:21 AM To: Lazar, Lijo Lijo.Lazar@amd.com; Koenig, Christian Christian.Koenig@amd.com; Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
On 2022-04-20 09:23, Lazar, Lijo wrote:
On 4/20/2022 6:26 PM, Christian König wrote:
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
- Change the test case to use something larger than 1TiB.
sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here. >
AFAIU, for the purpose of ttm use, fallback to vmalloc is fine.
- Please note that any use of gfp flags outside of GFP_KERNEL is
careful to not
- fall back to vmalloc.
That's weird, because kvcalloc does the same thing. If that were not able to fall back to vmalloc, it would be pretty useless.
static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t flags) { return kvmalloc_array(n, size, flags | __GFP_ZERO); }
Maybe kvcalloc is the function we TTM should be using here anyway, instead of open-coding the kvmalloc_array call with an extra GFP flag.
Regards, Felix
Yes, I agree with your point, and in amdkfd driver code, we have the same risk in svm_range_dma_map_dev().
Best Regards, Kevin
Actually the current implementation documents the behavior, but it is deep inside the implementation to be noticeable - at least not obvious while using kvmalloc_array.
Thanks, Lijo
Regards, Christian.
the system availed memory about 2T, but it will still fail.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 8:42 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is:
- Change the test case to use something larger than 1TiB.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; }DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com mailto:ckoenig.leichtzumerken@gmail.com *Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h... mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Koenig, Christian Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 5:00 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com; dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org mailto:dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org mailto:amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 10:56 schrieb Yang Wang: > if the __GFP_ZERO is set, the kvmalloc() can't fallback to use vmalloc()
Hui what? Why should kvmalloc() not be able to fallback to vmalloc() when __GFP_ZERO is set?
And even that is really the case then that sounds like a bug in kvmalloc().
Regards, Christian.
[kevin]: it is really test case from libdrm amdgpu test, which try to allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
it may be a kvmalloc() bug, and this patch can as a workaround in ttm before this issue fix.
void *kvmalloc_node(size_t size, gfp_t flags, int node) { ... if ((flags & GFP_KERNEL) != GFP_KERNEL) return kmalloc_node(size, flags, node); ... }
Best Regards, Kevin
> to allocate memory, when request size is exceeds kmalloc limit, it will > cause allocate memory fail. > > e.g: when ttm want to create a BO with 1TB size, it maybe fail. > > Signed-off-by: Yang Wang KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com > --- > drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c > index 79c870a3bef8..9f2f3e576b8d 100644 > --- a/drivers/gpu/drm/ttm/ttm_tt.c > +++ b/drivers/gpu/drm/ttm/ttm_tt.c > @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc) > static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) > { > ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->pages) > return -ENOMEM; > + > + memset(ttm->pages, 0, ttm->num_pages * sizeof(void *)); > + > return 0; > } > > @@ -108,10 +111,12 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) > ttm->pages = kvmalloc_array(ttm->num_pages, > sizeof(*ttm->pages) + > sizeof(*ttm->dma_address), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->pages) > return -ENOMEM; > > + memset(ttm->pages, 0, ttm->num_pages * (sizeof(*ttm->pages) + sizeof(*ttm->dma_address))); > + > ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); > return 0; > } > @@ -120,9 +125,12 @@ static int ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) > { > ttm->dma_address = kvmalloc_array(ttm->num_pages, > sizeof(*ttm->dma_address), > - GFP_KERNEL | __GFP_ZERO); > + GFP_KERNEL); > if (!ttm->dma_address) > return -ENOMEM; > + > + memset(ttm->dma_address, 0, ttm->num_pages * sizeof(*ttm->dma_address)); > + > return 0; > } >
Am 21.04.22 um 04:15 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
*From:* Kuehling, Felix Felix.Kuehling@amd.com *Sent:* Thursday, April 21, 2022 5:21 AM *To:* Lazar, Lijo Lijo.Lazar@amd.com; Koenig, Christian Christian.Koenig@amd.com; Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit
On 2022-04-20 09:23, Lazar, Lijo wrote:
On 4/20/2022 6:26 PM, Christian König wrote:
Am 20.04.22 um 14:54 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
- Change the test case to use something larger than 1TiB.
sure, we can increase the size of BO and make test pass, but if user really want to allocate 1TB GTT BO, we have no reason to let it fail? right?
No, the reason is the underlying core kernel doesn't allow kvmalloc allocations with GFP_ZERO which are large enough to hold the array of allocated pages for this.
We are working on top of the core Linux kernel and should *NEVER* ever add workarounds like what was suggested here. >
AFAIU, for the purpose of ttm use, fallback to vmalloc is fine.
* Please note that any use of gfp flags outside of GFP_KERNEL is careful to not * fall back to vmalloc. *
That's weird, because kvcalloc does the same thing. If that were not able to fall back to vmalloc, it would be pretty useless.
static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t flags) { return kvmalloc_array(n, size, flags | __GFP_ZERO); }
Maybe kvcalloc is the function we TTM should be using here anyway, instead of open-coding the kvmalloc_array call with an extra GFP flag.
Regards, Felix
Yes, I agree with your point, and in amdkfd driver code, we have the same risk in svm_range_dma_map_dev().
Yes, sounds like a good idea to me as well to change that.
Regards, Christian.
Best Regards, Kevin
Actually the current implementation documents the behavior, but it is deep inside the implementation to be noticeable - at least not obvious while using kvmalloc_array.
Thanks, Lijo
Regards, Christian.
the system availed memory about 2T, but it will still fail.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path. the 5.18 kernel will add this patch to fix this issue .
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com *Sent:* Wednesday, April 20, 2022 8:42 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com; Christian König ckoenig.leichtzumerken@gmail.com; dri-devel@lists.freedesktop.org dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org amd-gfx@lists.freedesktop.org *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
yes and that is perfectly valid and expected behavior. There is absolutely no need to change anything in TTM here.
What we could do is:
- Change the test case to use something larger than 1TiB.
- Change kvmalloc to allow GFP_ZERO allocations even in the vmalloc
fallback path.
Regards, Christian.
Am 20.04.22 um 14:39 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chirs,
yes, right, the amdgpu drive rwill use amdgpu_bo_validate_size() function to verify bo size, but when driver try to allocate VRAM domain bo fail, the amdgpu driver will fall back to allocate domain = (GTT | VRAM) bo. please check following code, it will cause the 2nd time to allocate bo fail during allocate 256Mb buffer to store dma address (via kvmalloc()).
initial_domain = (u32)(0xffffffff & args->in.domains); retry: r = amdgpu_gem_object_create(adev, size, args->in.alignment, initial_domain, flags, ttm_bo_type_device, resv, &gobj); if (r && r != -ERESTARTSYS) { if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED) { flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; goto retry; }
if (initial_domain == AMDGPU_GEM_DOMAIN_VRAM) { initial_domain |= AMDGPU_GEM_DOMAIN_GTT; goto retry; } DRM_DEBUG("Failed to allocate GEM object (%llu, %d, %llu, %d)\n", size, initial_domain, args->in.alignment, r); }
Best Regards, Kevin
*From:* Christian König ckoenig.leichtzumerken@gmail.com <mailto:ckoenig.leichtzumerken@gmail.com
mailto:ckoenig.leichtzumerken@gmail.com>
*Sent:* Wednesday, April 20, 2022 7:55 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com <mailto:KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com>;
Koenig, Christian
Christian.Koenig@amd.com <mailto:Christian.Koenig@amd.com
mailto:Christian.Koenig@amd.com>;
dri-devel@lists.freedesktop.org <mailto:dri-devel@lists.freedesktop.org
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*Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Hi Kevin,
no, the test case should already fail in amdgpu_bo_validate_size().
If we have a system with 2TiB of memory where the test case could succeed then we should increase the requested size to something larger.
And if the underlying core Linux kernel functions don't allow allocations as large as the requested one we should *NEVER* ever add workarounds like this.
It is perfectly expected that this test case is not able to fulfill the desired allocation. That it fails during kvmalloc is unfortunate, but not a show stopper.
Regards, Christian.
Am 20.04.22 um 13:32 schrieb Wang, Yang(Kevin):
[AMD Official Use Only]
Hi Chris,
you misunderstood background about this case.
although we expect this test case to fail, it should fail at the location where the Bo actual memory is actually allocated. now the code logic will cause the failure to allocate memory to store DMA address.
e.g: the case is failed in 2TB system ram machine, it should be allocated successful, but it is failed.
allocate 1TB BO, the ttm should allocate 1TB/4k * 8 buffer to store allocate result (page address), this should not be failed usually.
There is a similar fix in upstream kernel 5.18, before this fix entered the TTM code, this problem existed in TTM.
kernel/git/torvalds/linux.git - Linux kernel source tree
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h...
mm: allow !GFP_KERNEL allocations for kvmalloc
Best Regards, Kevin
*From:* Koenig, Christian Christian.Koenig@amd.com <mailto:Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com> *Sent:* Wednesday, April 20, 2022 6:53 PM *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com <mailto:KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com>;
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*Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size exceeds kmalloc limit Am 20.04.22 um 11:07 schrieb Wang, Yang(Kevin): > > [AMD Official Use Only] > > > >
> > *From:* Koenig, Christian Christian.Koenig@amd.com > <mailto:Christian.Koenig@amd.com mailto:Christian.Koenig@amd.com> > *Sent:* Wednesday, April 20, 2022 5:00 PM > *To:* Wang, Yang(Kevin) KevinYang.Wang@amd.com > <mailto:KevinYang.Wang@amd.com
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> *Subject:* Re: [PATCH] drm/ttm: fix ttm tt init fail when size > exceeds kmalloc limit > Am 20.04.22 um 10:56 schrieb Yang Wang: > > if the __GFP_ZERO is set, the kvmalloc() can't fallback to use > vmalloc() > > Hui what? Why should kvmalloc() not be able to fallback to
vmalloc()
> when __GFP_ZERO is set? > > And even that is really the case then that sounds like a bug in > kvmalloc(). > > Regards, > Christian. > > [kevin]: > it is really test case from libdrm amdgpu test, which try to > allocate a big BO which will cause ttm tt init fail.
LOL! Guys, this test case is intended to fail!
*The test consists of allocating a buffer so ridiculous large that it should never succeed and be rejected by the kernel driver.
This patch here is a really clear NAK.
Regards, Christian.
> it may be a kvmalloc() bug, and this patch can as a workaround > in ttm before this issue fix. > > void *kvmalloc_node(size_t size, gfp_t flags, int node) > { > ... > if ((flags & GFP_KERNEL) != GFP_KERNEL) > return kmalloc_node(size, flags, node); > ... > } > > Best Regards, > Kevin > > > to allocate memory, when request size is exceeds kmalloc limit, > it will > > cause allocate memory fail. > > > > e.g: when ttm want to create a BO with 1TB size, it maybe fail. > > > > Signed-off-by: Yang Wang KevinYang.Wang@amd.com > <mailto:KevinYang.Wang@amd.com mailto:KevinYang.Wang@amd.com> > > --- > > drivers/gpu/drm/ttm/ttm_tt.c | 14 +++++++++++--- > > 1 file changed, 11 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/gpu/drm/ttm/ttm_tt.c > b/drivers/gpu/drm/ttm/ttm_tt.c > > index 79c870a3bef8..9f2f3e576b8d 100644 > > --- a/drivers/gpu/drm/ttm/ttm_tt.c > > +++ b/drivers/gpu/drm/ttm/ttm_tt.c > > @@ -97,9 +97,12 @@ int ttm_tt_create(struct ttm_buffer_object > *bo, bool zero_alloc) > > static int ttm_tt_alloc_page_directory(struct ttm_tt *ttm) > > { > > ttm->pages = kvmalloc_array(ttm->num_pages, sizeof(void*), > > - GFP_KERNEL | __GFP_ZERO); > > + GFP_KERNEL); > > if (!ttm->pages) > > return -ENOMEM; > > + > > + memset(ttm->pages, 0, ttm->num_pages * sizeof(void *)); > > + > > return 0; > > } > > > > @@ -108,10 +111,12 @@ static int > ttm_dma_tt_alloc_page_directory(struct ttm_tt *ttm) > > ttm->pages = kvmalloc_array(ttm->num_pages, > > sizeof(*ttm->pages) + > > sizeof(*ttm->dma_address), > > - GFP_KERNEL | __GFP_ZERO); > > + GFP_KERNEL); > > if (!ttm->pages) > > return -ENOMEM; > > > > + memset(ttm->pages, 0, ttm->num_pages * > (sizeof(*ttm->pages) + sizeof(*ttm->dma_address))); > > + > > ttm->dma_address = (void *)(ttm->pages + ttm->num_pages); > > return 0; > > } > > @@ -120,9 +125,12 @@ static int > ttm_sg_tt_alloc_page_directory(struct ttm_tt *ttm) > > { > > ttm->dma_address = kvmalloc_array(ttm->num_pages, > > sizeof(*ttm->dma_address), > > - GFP_KERNEL | __GFP_ZERO); > > + GFP_KERNEL); > > if (!ttm->dma_address) > > return -ENOMEM; > > + > > + memset(ttm->dma_address, 0, ttm->num_pages * > sizeof(*ttm->dma_address)); > > + > > return 0; > > } > > >
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