On 14/11/2021 11:12, Thomas Hellström wrote:

From: Maarten Lankhorst maarten.lankhorst@linux.intel.com

We want to get rid of i915_vma tracking to simplify the code and lifetimes. Add a way to set/put the moving fence, in preparation for removing the tracking.

Signed-off-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_object.c | 37 ++++++++++++++++++++++ drivers/gpu/drm/i915/gem/i915_gem_object.h | 9 ++++++ 2 files changed, 46 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c index 591ee3cb7275..ec4313836597 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c @@ -33,6 +33,7 @@ #include "i915_gem_object.h" #include "i915_memcpy.h" #include "i915_trace.h" +#include "i915_gem_ttm.h"

static struct kmem_cache *slab_objects;

@@ -726,6 +727,42 @@ static const struct drm_gem_object_funcs i915_gem_object_funcs = { .export = i915_gem_prime_export, };

+struct dma_fence * +i915_gem_object_get_moving_fence(struct drm_i915_gem_object *obj) +{

• return dma_fence_get(i915_gem_to_ttm(obj)->moving);

+}

+void i915_gem_object_set_moving_fence(struct drm_i915_gem_object *obj,

• 		      struct dma_fence *fence)
  

+{

• dma_fence_put(i915_gem_to_ttm(obj)->moving);
• i915_gem_to_ttm(obj)->moving = dma_fence_get(fence);

+}

Are these also assert_object_held()? Should we maybe squash this patch with the first user?

+int i915_gem_object_wait_moving_fence(struct drm_i915_gem_object *obj,

• 		      bool intr)
  

+{

• struct dma_fence *fence = i915_gem_to_ttm(obj)->moving;
• int ret;
• assert_object_held(obj);
• if (!fence)

• return 0;
  

• ret = dma_fence_wait(fence, intr);
• if (ret)

• return ret;
  

• if (fence->error)

• return fence->error;
  

• i915_gem_to_ttm(obj)->moving = NULL;
• dma_fence_put(fence);
• return 0;

+}

• #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) #include "selftests/huge_gem_object.c" #include "selftests/huge_pages.c"

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h index 133963b46135..36bf3e2e602f 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h @@ -517,6 +517,15 @@ i915_gem_object_finish_access(struct drm_i915_gem_object *obj) i915_gem_object_unpin_pages(obj); }

+struct dma_fence * +i915_gem_object_get_moving_fence(struct drm_i915_gem_object *obj);

+void i915_gem_object_set_moving_fence(struct drm_i915_gem_object *obj,

• 		      struct dma_fence *fence);
  

+int i915_gem_object_wait_moving_fence(struct drm_i915_gem_object *obj,

• 		      bool intr);
  

• void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj, unsigned int cache_level); bool i915_gem_object_can_bypass_llc(struct drm_i915_gem_object *obj);

On 11/15/21 13:36, Matthew Auld wrote:

On 14/11/2021 11:12, Thomas Hellström wrote:

...

From: Maarten Lankhorst maarten.lankhorst@linux.intel.com

For now, we will only allow async migration when TTM is used, so the paths we care about are related to TTM.

The mmap path is handled by having the fence in ttm_bo->moving, when pinning, the binding only becomes available after the moving fence is signaled, and pinning a cpu map will only work after the moving fence signals.

This should close all holes where userspace can read a buffer before it's fully migrated.

v2:

• Fix a couple of SPARSE warnings

v3:

• Fix a NULL pointer dereference

Co-developed-by: Thomas Hellström thomas.hellstrom@linux.intel.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com Signed-off-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com

---

drivers/gpu/drm/i915/display/intel_fbdev.c    |  7 ++--   drivers/gpu/drm/i915/display/intel_overlay.c  |  2 +-   drivers/gpu/drm/i915/gem/i915_gem_pages.c     |  6 +++   .../i915/gem/selftests/i915_gem_coherency.c   |  4 +-   .../drm/i915/gem/selftests/i915_gem_mman.c    | 22 ++++++-----   drivers/gpu/drm/i915/i915_vma.c               | 39 ++++++++++++++++++-   drivers/gpu/drm/i915/i915_vma.h               |  3 ++   drivers/gpu/drm/i915/selftests/i915_vma.c     |  4 +-   8 files changed, 69 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c index adc3a81be9f7..5902ad0c2bd8 100644 --- a/drivers/gpu/drm/i915/display/intel_fbdev.c +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c @@ -265,11 +265,12 @@ static int intelfb_create(struct drm_fb_helper *helper,           info->fix.smem_len = vma->node.size;       }   -    vaddr = i915_vma_pin_iomap(vma); +    vaddr = i915_vma_pin_iomap_unlocked(vma);       if (IS_ERR(vaddr)) { -        drm_err(&dev_priv->drm, -            "Failed to remap framebuffer into virtual memory\n");           ret = PTR_ERR(vaddr); +        if (ret != -EINTR && ret != -ERESTARTSYS) +            drm_err(&dev_priv->drm, +                "Failed to remap framebuffer into virtual memory\n");           goto out_unpin;       }       info->screen_base = vaddr; diff --git a/drivers/gpu/drm/i915/display/intel_overlay.c b/drivers/gpu/drm/i915/display/intel_overlay.c index 7e3f5c6ca484..21593f3f2664 100644 --- a/drivers/gpu/drm/i915/display/intel_overlay.c +++ b/drivers/gpu/drm/i915/display/intel_overlay.c @@ -1357,7 +1357,7 @@ static int get_registers(struct intel_overlay *overlay, bool use_phys)           overlay->flip_addr = sg_dma_address(obj->mm.pages->sgl);       else           overlay->flip_addr = i915_ggtt_offset(vma); -    overlay->regs = i915_vma_pin_iomap(vma); +    overlay->regs = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);         if (IS_ERR(overlay->regs)) { diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c index c4f684b7cc51..49c6e55c68ce 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c @@ -418,6 +418,12 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,       }         if (!ptr) { +        err = i915_gem_object_wait_moving_fence(obj, true); +        if (err) { +            ptr = ERR_PTR(err); +            goto err_unpin; +        }

if (GEM_WARN_ON(type == I915_MAP_WC &&                   !static_cpu_has(X86_FEATURE_PAT)))               ptr = ERR_PTR(-ENODEV); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c index 13b088cc787e..067c512961ba 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c @@ -101,7 +101,7 @@ static int gtt_set(struct context *ctx, unsigned long offset, u32 v)         intel_gt_pm_get(vma->vm->gt);   -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); @@ -134,7 +134,7 @@ static int gtt_get(struct context *ctx, unsigned long offset, u32 *v)         intel_gt_pm_get(vma->vm->gt);   -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c index 6d30cdfa80f3..5d54181c2145 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c @@ -125,12 +125,13 @@ static int check_partial_mapping(struct drm_i915_gem_object *obj,       n = page - view.partial.offset;       GEM_BUG_ON(n >= view.partial.size);   -    io = i915_vma_pin_iomap(vma); +    io = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(io)) { -        pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", -               page, (int)PTR_ERR(io));           err = PTR_ERR(io); +        if (err != -EINTR && err != -ERESTARTSYS) +            pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", +                   page, err);           goto out;       }   @@ -219,12 +220,15 @@ static int check_partial_mappings(struct drm_i915_gem_object *obj,           n = page - view.partial.offset;           GEM_BUG_ON(n >= view.partial.size);   -        io = i915_vma_pin_iomap(vma); +        io = i915_vma_pin_iomap_unlocked(vma);           i915_vma_unpin(vma);           if (IS_ERR(io)) { -            pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", -                   page, (int)PTR_ERR(io)); -            return PTR_ERR(io); +            int err = PTR_ERR(io);

+            if (err != -EINTR && err != -ERESTARTSYS) +                pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", +                       page, err); +            return err;           }             iowrite32(page, io + n * PAGE_SIZE / sizeof(*io)); @@ -773,7 +777,7 @@ static int gtt_set(struct drm_i915_gem_object *obj)           return PTR_ERR(vma);         intel_gt_pm_get(vma->vm->gt); -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); @@ -799,7 +803,7 @@ static int gtt_check(struct drm_i915_gem_object *obj)           return PTR_ERR(vma);         intel_gt_pm_get(vma->vm->gt); -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index 8781c4f61952..069f22b3cd48 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -431,6 +431,13 @@ int i915_vma_bind(struct i915_vma *vma,               work->pinned = i915_gem_object_get(vma->obj);           }       } else { +        if (vma->obj) { +            int ret;

+            ret = i915_gem_object_wait_moving_fence(vma->obj, true); +            if (ret) +                return ret; +        }           vma->ops->bind_vma(vma->vm, NULL, vma, cache_level, bind_flags);       }   @@ -455,6 +462,10 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)         ptr = READ_ONCE(vma->iomap);       if (ptr == NULL) { +        err = i915_gem_object_wait_moving_fence(vma->obj, true); +        if (err) +            goto err;

/*            * TODO: consider just using i915_gem_object_pin_map() for lmem            * instead, which already supports mapping non-contiguous chunks @@ -496,6 +507,25 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)       return IO_ERR_PTR(err);   }   +void __iomem *i915_vma_pin_iomap_unlocked(struct i915_vma *vma) +{ +    struct i915_gem_ww_ctx ww; +    void __iomem *map; +    int err;

+    for_i915_gem_ww(&ww, err, true) { +        err = i915_gem_object_lock(vma->obj, &ww); +        if (err) +            continue;

+        map = i915_vma_pin_iomap(vma); +    } +    if (err) +        map = IO_ERR_PTR(err);

+    return map; +}

What is the reason for this change? Is this strictly related to this series/commit?

Yes, it's because pulling out the moving fence requires the dma_resv lock.

/Thomas

On 11/15/21 14:13, Matthew Auld wrote:

On 15/11/2021 12:42, Thomas Hellström wrote:

...

On 11/15/21 13:36, Matthew Auld wrote:

...

On 14/11/2021 11:12, Thomas Hellström wrote:

...

From: Maarten Lankhorst maarten.lankhorst@linux.intel.com

For now, we will only allow async migration when TTM is used, so the paths we care about are related to TTM.

The mmap path is handled by having the fence in ttm_bo->moving, when pinning, the binding only becomes available after the moving fence is signaled, and pinning a cpu map will only work after the moving fence signals.

This should close all holes where userspace can read a buffer before it's fully migrated.

v2:

• Fix a couple of SPARSE warnings

v3:

• Fix a NULL pointer dereference

Co-developed-by: Thomas Hellström thomas.hellstrom@linux.intel.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com Signed-off-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com

---

drivers/gpu/drm/i915/display/intel_fbdev.c    |  7 ++--   drivers/gpu/drm/i915/display/intel_overlay.c  |  2 +-   drivers/gpu/drm/i915/gem/i915_gem_pages.c     |  6 +++   .../i915/gem/selftests/i915_gem_coherency.c   |  4 +-   .../drm/i915/gem/selftests/i915_gem_mman.c    | 22 ++++++-----   drivers/gpu/drm/i915/i915_vma.c               | 39 ++++++++++++++++++-   drivers/gpu/drm/i915/i915_vma.h               |  3 ++   drivers/gpu/drm/i915/selftests/i915_vma.c     |  4 +-   8 files changed, 69 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c index adc3a81be9f7..5902ad0c2bd8 100644 --- a/drivers/gpu/drm/i915/display/intel_fbdev.c +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c @@ -265,11 +265,12 @@ static int intelfb_create(struct drm_fb_helper *helper,           info->fix.smem_len = vma->node.size;       }   -    vaddr = i915_vma_pin_iomap(vma); +    vaddr = i915_vma_pin_iomap_unlocked(vma);       if (IS_ERR(vaddr)) { -        drm_err(&dev_priv->drm, -            "Failed to remap framebuffer into virtual memory\n");           ret = PTR_ERR(vaddr); +        if (ret != -EINTR && ret != -ERESTARTSYS) +            drm_err(&dev_priv->drm, +                "Failed to remap framebuffer into virtual memory\n");           goto out_unpin;       }       info->screen_base = vaddr; diff --git a/drivers/gpu/drm/i915/display/intel_overlay.c b/drivers/gpu/drm/i915/display/intel_overlay.c index 7e3f5c6ca484..21593f3f2664 100644 --- a/drivers/gpu/drm/i915/display/intel_overlay.c +++ b/drivers/gpu/drm/i915/display/intel_overlay.c @@ -1357,7 +1357,7 @@ static int get_registers(struct intel_overlay *overlay, bool use_phys)           overlay->flip_addr = sg_dma_address(obj->mm.pages->sgl);       else           overlay->flip_addr = i915_ggtt_offset(vma); -    overlay->regs = i915_vma_pin_iomap(vma); +    overlay->regs = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);         if (IS_ERR(overlay->regs)) { diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c index c4f684b7cc51..49c6e55c68ce 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c @@ -418,6 +418,12 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,       }         if (!ptr) { +        err = i915_gem_object_wait_moving_fence(obj, true); +        if (err) { +            ptr = ERR_PTR(err); +            goto err_unpin; +        }

if (GEM_WARN_ON(type == I915_MAP_WC &&                   !static_cpu_has(X86_FEATURE_PAT)))               ptr = ERR_PTR(-ENODEV); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c index 13b088cc787e..067c512961ba 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c @@ -101,7 +101,7 @@ static int gtt_set(struct context *ctx, unsigned long offset, u32 v)         intel_gt_pm_get(vma->vm->gt);   -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); @@ -134,7 +134,7 @@ static int gtt_get(struct context *ctx, unsigned long offset, u32 *v)         intel_gt_pm_get(vma->vm->gt);   -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c index 6d30cdfa80f3..5d54181c2145 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c @@ -125,12 +125,13 @@ static int check_partial_mapping(struct drm_i915_gem_object *obj,       n = page - view.partial.offset;       GEM_BUG_ON(n >= view.partial.size);   -    io = i915_vma_pin_iomap(vma); +    io = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(io)) { -        pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", -               page, (int)PTR_ERR(io));           err = PTR_ERR(io); +        if (err != -EINTR && err != -ERESTARTSYS) +            pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", +                   page, err);           goto out;       }   @@ -219,12 +220,15 @@ static int check_partial_mappings(struct drm_i915_gem_object *obj,           n = page - view.partial.offset;           GEM_BUG_ON(n >= view.partial.size);   -        io = i915_vma_pin_iomap(vma); +        io = i915_vma_pin_iomap_unlocked(vma);           i915_vma_unpin(vma);           if (IS_ERR(io)) { -            pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", -                   page, (int)PTR_ERR(io)); -            return PTR_ERR(io); +            int err = PTR_ERR(io);

+            if (err != -EINTR && err != -ERESTARTSYS) +                pr_err("Failed to iomap partial view: offset=%lu; err=%d\n", +                       page, err); +            return err;           }             iowrite32(page, io + n * PAGE_SIZE / sizeof(*io)); @@ -773,7 +777,7 @@ static int gtt_set(struct drm_i915_gem_object *obj)           return PTR_ERR(vma);         intel_gt_pm_get(vma->vm->gt); -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); @@ -799,7 +803,7 @@ static int gtt_check(struct drm_i915_gem_object *obj)           return PTR_ERR(vma);         intel_gt_pm_get(vma->vm->gt); -    map = i915_vma_pin_iomap(vma); +    map = i915_vma_pin_iomap_unlocked(vma);       i915_vma_unpin(vma);       if (IS_ERR(map)) {           err = PTR_ERR(map); diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index 8781c4f61952..069f22b3cd48 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -431,6 +431,13 @@ int i915_vma_bind(struct i915_vma *vma,               work->pinned = i915_gem_object_get(vma->obj);           }       } else { +        if (vma->obj) { +            int ret;

+            ret = i915_gem_object_wait_moving_fence(vma->obj, true); +            if (ret) +                return ret; +        }           vma->ops->bind_vma(vma->vm, NULL, vma, cache_level, bind_flags);       }   @@ -455,6 +462,10 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)         ptr = READ_ONCE(vma->iomap);       if (ptr == NULL) { +        err = i915_gem_object_wait_moving_fence(vma->obj, true); +        if (err) +            goto err;

/*            * TODO: consider just using i915_gem_object_pin_map() for lmem            * instead, which already supports mapping non-contiguous chunks @@ -496,6 +507,25 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)       return IO_ERR_PTR(err);   }   +void __iomem *i915_vma_pin_iomap_unlocked(struct i915_vma *vma) +{ +    struct i915_gem_ww_ctx ww; +    void __iomem *map; +    int err;

+    for_i915_gem_ww(&ww, err, true) { +        err = i915_gem_object_lock(vma->obj, &ww); +        if (err) +            continue;

+        map = i915_vma_pin_iomap(vma); +    } +    if (err) +        map = IO_ERR_PTR(err);

+    return map; +}

What is the reason for this change? Is this strictly related to this series/commit?

Yes, it's because pulling out the moving fence requires the dma_resv lock.

Ok, I was thinking that vma_pin_iomap is only ever called on an already bound GGTT vma, for which we do a syncronous wait_for_bind, but maybe that's not always true?

Hmm, Good point. We should probably replace that vma_pin_iomap stuff with an assert that the binding fence is indeed signaled and error free? Because if binding succeeded, no need to check the moving fence.

/Thomas

Reviewed-by: Matthew Auld matthew.auld@intel.com

...

/Thomas

On 14/11/2021 11:12, Thomas Hellström wrote:

There is an interesting refcounting loop: struct intel_memory_region has a struct ttm_resource_manager, ttm_resource_manager->move may hold a reference to i915_request, i915_request may hold a reference to intel_context, intel_context may hold a reference to drm_i915_gem_object, drm_i915_gem_object may hold a reference to intel_memory_region.

Would it help if we drop the per object region refcoutning? IIRC that was originally added to more cleanly appease some selftest teardown or something.

Break this loop when we drop the device reference count on the region by putting the region move fence.

Also hold dropping the device reference count until all objects of the region has been deleted, to avoid issues if proceeding with the device takedown while the region is still present.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 1 + drivers/gpu/drm/i915/gt/intel_region_lmem.c | 1 + drivers/gpu/drm/i915/intel_memory_region.c | 5 +++- drivers/gpu/drm/i915/intel_memory_region.h | 1 + drivers/gpu/drm/i915/intel_region_ttm.c | 28 +++++++++++++++++++++ drivers/gpu/drm/i915/intel_region_ttm.h | 2 ++ 6 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index 537a81445b90..a1df49378a0f 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -1044,6 +1044,7 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,

static const struct intel_memory_region_ops ttm_system_region_ops = { .init_object = __i915_gem_ttm_object_init,

• .disable = intel_region_ttm_disable, };

  struct intel_memory_region *

diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c index aec838ecb2ef..956916fd21f8 100644 --- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c +++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c @@ -108,6 +108,7 @@ region_lmem_init(struct intel_memory_region *mem) static const struct intel_memory_region_ops intel_region_lmem_ops = { .init = region_lmem_init, .release = region_lmem_release,

• .disable = intel_region_ttm_disable, .init_object = __i915_gem_ttm_object_init, };

diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c index e7f7e6627750..1f67d2b68c24 100644 --- a/drivers/gpu/drm/i915/intel_memory_region.c +++ b/drivers/gpu/drm/i915/intel_memory_region.c @@ -233,8 +233,11 @@ void intel_memory_regions_driver_release(struct drm_i915_private *i915) struct intel_memory_region *region = fetch_and_zero(&i915->mm.regions[i]);

• if (region)
  

• if (region) {
  

• 	if (region->ops->disable)
  

• 		region->ops->disable(region);
  intel_memory_region_put(region);
  

• }
  

  } }

diff --git a/drivers/gpu/drm/i915/intel_memory_region.h b/drivers/gpu/drm/i915/intel_memory_region.h index 3feae3353d33..9bb77eacd206 100644 --- a/drivers/gpu/drm/i915/intel_memory_region.h +++ b/drivers/gpu/drm/i915/intel_memory_region.h @@ -52,6 +52,7 @@ struct intel_memory_region_ops {

int (*init)(struct intel_memory_region *mem); void (*release)(struct intel_memory_region *mem);

• void (*disable)(struct intel_memory_region *mem);

  int (*init_object)(struct intel_memory_region *mem, struct drm_i915_gem_object *obj,

diff --git a/drivers/gpu/drm/i915/intel_region_ttm.c b/drivers/gpu/drm/i915/intel_region_ttm.c index 2e901a27e259..4219d83a2b19 100644 --- a/drivers/gpu/drm/i915/intel_region_ttm.c +++ b/drivers/gpu/drm/i915/intel_region_ttm.c @@ -114,6 +114,34 @@ void intel_region_ttm_fini(struct intel_memory_region *mem) mem->region_private = NULL; }

+/**

• • intel_region_ttm_disable - A TTM region disable callback helper
• • @mem: The memory region.
• • A helper that ensures that nothing any longer references a region at
• • device takedown. Breaks refcounting loops and waits for objects in the
• • region to be deleted.
• */

+void intel_region_ttm_disable(struct intel_memory_region *mem) +{

• struct ttm_resource_manager *man = mem->region_private;
• /*

• * Put the region's move fences. This releases requests that
  

• * may hold on to contexts and vms that may hold on to buffer
  

• * objects that may have a refcount on the region. :/
  

• */
  

• if (man)

• ttm_resource_manager_cleanup(man);
  

• /* Flush objects that may just have been freed */
• i915_gem_flush_free_objects(mem->i915);
• /* Wait until the only region reference left is our own. */
• while (kref_read(&mem->kref) > 1)

• msleep(20);
  

If we leak an object, I guess we get an infinite loop here at driver release?

+}

• /**
  • intel_region_ttm_resource_to_rsgt -
  • Convert an opaque TTM resource manager resource to a refcounted sg_table.

diff --git a/drivers/gpu/drm/i915/intel_region_ttm.h b/drivers/gpu/drm/i915/intel_region_ttm.h index 7bbe2b46b504..197a8c179370 100644 --- a/drivers/gpu/drm/i915/intel_region_ttm.h +++ b/drivers/gpu/drm/i915/intel_region_ttm.h @@ -22,6 +22,8 @@ int intel_region_ttm_init(struct intel_memory_region *mem);

void intel_region_ttm_fini(struct intel_memory_region *mem);

+void intel_region_ttm_disable(struct intel_memory_region *mem);

• struct i915_refct_sgt * intel_region_ttm_resource_to_rsgt(struct intel_memory_region *mem, struct ttm_resource *res);

On 14/11/2021 11:12, Thomas Hellström wrote:

Don't wait sync while migrating, but rather make the GPU blit await the dependencies and add a moving fence to the object.

This also enables asynchronous VRAM management in that on eviction, rather than waiting for the moving fence to expire before freeing VRAM, it is freed immediately and the fence is stored with the VRAM manager and handed out to newly allocated objects to await before clears and swapins, or for kernel objects before setting up gpu vmas or mapping.

To collect dependencies before migrating, add a set of utilities that coalesce these to a single dma_fence.

What is still missing for fully asynchronous operation is asynchronous vma unbinding, which is still to be implemented.

This commit substantially reduces execution time in the gem_lmem_swapping test.

v2:

• Make a couple of functions static.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 10 + drivers/gpu/drm/i915/gem/i915_gem_ttm.h | 2 +- drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 329 +++++++++++++++++-- drivers/gpu/drm/i915/gem/i915_gem_wait.c | 4 +- 4 files changed, 318 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index a1df49378a0f..111a4282d779 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -326,6 +326,9 @@ static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo, { struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

• if (!obj)

• return false;
  

• /*
  • EXTERNAL objects should never be swapped out by TTM, instead we need
  • to handle that ourselves. TTM will already skip such objects for us,

@@ -448,6 +451,10 @@ static int i915_ttm_shrinker_release_pages(struct drm_i915_gem_object *obj, if (bo->ttm->page_flags & TTM_TT_FLAG_SWAPPED) return 0;

• ret = ttm_bo_wait_ctx(bo, &ctx);
• if (ret)

• return ret;
  

Why do we need this? Also not needed for the above purge case?

• bo->ttm->page_flags |= TTM_TT_FLAG_SWAPPED; ret = ttm_bo_validate(bo, &place, &ctx); if (ret) {

@@ -549,6 +556,9 @@ static void i915_ttm_swap_notify(struct ttm_buffer_object *bo) struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo); int ret = i915_ttm_move_notify(bo);

• if (!obj)

• return;
  

It looks like the i915_ttm_move_notify(bo) already dereferenced the GEM bo. Or did something in there maybe nuke it?

• GEM_WARN_ON(ret); GEM_WARN_ON(obj->ttm.cached_io_rsgt); if (!ret && obj->mm.madv != I915_MADV_WILLNEED)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h index 82cdabb542be..9d698ad00853 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h @@ -37,7 +37,7 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo); static inline struct drm_i915_gem_object * i915_ttm_to_gem(struct ttm_buffer_object *bo) {

• if (GEM_WARN_ON(bo->destroy != i915_ttm_bo_destroy))

• if (bo->destroy != i915_ttm_bo_destroy) return NULL;

So this would indicate a "ghost" object, or is this something else? How scared should we be with this, like with the above checking for NULL GEM object state? In general do you know where we need the above checking?

return container_of(bo, struct drm_i915_gem_object, __do_not_access); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c index f35b386c56ca..ae2c49fc3500 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c @@ -3,6 +3,8 @@

• Copyright © 2021 Intel Corporation

*/

+#include <linux/dma-fence-array.h>

• #include <drm/ttm/ttm_bo_driver.h>

  #include "i915_drv.h"

@@ -41,6 +43,228 @@ void i915_ttm_migrate_set_failure_modes(bool gpu_migration, } #endif

+/**

• • DOC: Set of utilities to dynamically collect dependencies and
• • eventually coalesce them into a single fence which is fed into
• • the migration code. That single fence is, in the case of dependencies
• • from multiple contexts, a struct dma_fence_array, since the
• • i915 request code can break that up and await the individual
• • fences.

Would it make sense to add few more more details here for why we need this? IIUC it looks like TTM expects single context/timeline for pipelined move, like with that dma_fence_is_later() check in pipeline_evict? Maybe there is something already documented in TTM we can link to here?

• • While collecting the individual dependencies, we store the refcounted
• • struct dma_fence pointers in a realloc-type-managed pointer array, since
• • that can be easily fed into a dma_fence_array. Other options are
• • available, like for example an xarray for similarity with drm/sched.
• • Can be changed easily if needed.
• • We might want to break this out into a separate file as a utility.
• */

+#define I915_DEPS_MIN_ALLOC_CHUNK 8U

+/**

• • struct i915_deps - Collect dependencies into a single dma-fence
• • @single: Storage for pointer if the collection is a single fence.
• • @fence: Allocated array of fence pointers if more than a single fence;
• • otherwise points to the address of @single.
• • @num_deps: Current number of dependency fences.
• • @fences_size: Size of the @fences array in number of pointers.
• • @gfp: Allocation mode.
• */

+struct i915_deps {

• struct dma_fence *single;
• struct dma_fence **fences;
• unsigned int num_deps;
• unsigned int fences_size;
• gfp_t gfp;

+};

+static void i915_deps_reset_fences(struct i915_deps *deps) +{

• if (deps->fences != &deps->single)

• kfree(deps->fences);
  

• deps->num_deps = 0;
• deps->fences_size = 1;
• deps->fences = &deps->single;

+}

+static void i915_deps_init(struct i915_deps *deps, gfp_t gfp) +{

• deps->fences = NULL;
• deps->gfp = gfp;
• i915_deps_reset_fences(deps);

+}

+static void i915_deps_fini(struct i915_deps *deps) +{

• unsigned int i;
• for (i = 0; i < deps->num_deps; ++i)

• dma_fence_put(deps->fences[i]);
  

• if (deps->fences != &deps->single)

• kfree(deps->fences);
  

+}

+static int i915_deps_grow(struct i915_deps *deps, struct dma_fence *fence,

• 	  const struct ttm_operation_ctx *ctx)
  

+{

• int ret;
• if (deps->num_deps >= deps->fences_size) {

• unsigned int new_size = 2 * deps->fences_size;
  

• struct dma_fence **new_fences;
  

• new_size = max(new_size, I915_DEPS_MIN_ALLOC_CHUNK);
  

• new_fences = kmalloc_array(new_size, sizeof(*new_fences), deps->gfp);
  

• if (!new_fences)
  

• 	goto sync;
  

• memcpy(new_fences, deps->fences,
  

•        deps->fences_size * sizeof(*new_fences));
  

• swap(new_fences, deps->fences);
  

• if (new_fences != &deps->single)
  

• 	kfree(new_fences);
  

• deps->fences_size = new_size;
  

• }
• deps->fences[deps->num_deps++] = dma_fence_get(fence);
• return 0;

+sync:

• if (ctx->no_wait_gpu) {

• ret = -EBUSY;
  

• goto unref;
  

• }
• ret = dma_fence_wait(fence, ctx->interruptible);
• if (ret)

• goto unref;
  

• ret = fence->error;
• if (ret)

• goto unref;
  

• return 0;

+unref:

• i915_deps_fini(deps);
• return ret;

+}

+static int i915_deps_sync(struct i915_deps *deps,

• 	  const struct ttm_operation_ctx *ctx)
  

+{

• unsigned int i;
• int ret = 0;
• struct dma_fence **fences = deps->fences;

Nit: Christmas tree.

• for (i = 0; i < deps->num_deps; ++i, ++fences) {

• if (ctx->no_wait_gpu) {
  

• 	ret = -EBUSY;
  

• 	goto unref;
  

• }
  

• ret = dma_fence_wait(*fences, ctx->interruptible);
  

• if (ret)
  

• 	goto unref;
  

• ret = (*fences)->error;
  

• if (ret)
  

• 	goto unref;
  

• }
• i915_deps_fini(deps);
• return 0;

+unref:

• i915_deps_fini(deps);
• return ret;

+}

+static int i915_deps_add_dependency(struct i915_deps *deps,

• 		    struct dma_fence *fence,
  

• 		    const struct ttm_operation_ctx *ctx)
  

+{

• unsigned int i;
• int ret;
• if (!fence)

• return 0;
  

• if (dma_fence_is_signaled(fence)) {

• ret = fence->error;
  

• if (ret)
  

• 	i915_deps_fini(deps);
  

• return ret;
  

• }
• for (i = 0; i < deps->num_deps; ++i) {

• struct dma_fence *entry = deps->fences[i];
  

• if (!entry->context || entry->context != fence->context)
  

• 	continue;
  

• if (dma_fence_is_later(fence, entry)) {
  

• 	dma_fence_put(entry);
  

• 	deps->fences[i] = dma_fence_get(fence);
  

• }
  

• return 0;
  

• }
• return i915_deps_grow(deps, fence, ctx);

+}

+static struct dma_fence *i915_deps_to_fence(struct i915_deps *deps,

• 			    const struct ttm_operation_ctx *ctx)
  

+{

• struct dma_fence_array *array;
• if (deps->num_deps == 0)

• return NULL;
  

• if (deps->num_deps == 1) {

• deps->num_deps = 0;
  

• return deps->fences[0];
  

• }
• /*

• * TODO: Alter the allocation mode here to not try too hard to
  

• * make things async.
  

• */
  

• array = dma_fence_array_create(deps->num_deps, deps->fences, 0, 0,

• 		       false);
  

• if (!array)

• return ERR_PTR(i915_deps_sync(deps, ctx));
  

• deps->fences = NULL;
• i915_deps_reset_fences(deps);
• return &array->base;

+}

+static int i915_deps_add_resv(struct i915_deps *deps, struct dma_resv *resv,

• 	      bool all, const bool no_excl,
  

• 	      const struct ttm_operation_ctx *ctx)
  

+{

• struct dma_resv_iter iter;
• struct dma_fence *fence;
• dma_resv_assert_held(resv);
• dma_resv_for_each_fence(&iter, resv, all, fence) {

• int ret;
  

• if (no_excl && !iter.index)
  

• 	continue;
  

• ret = i915_deps_add_dependency(deps, fence, ctx);
  

• if (ret)
  

• 	return ret;
  

• }
• return 0;

+}

• static enum i915_cache_level i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res, struct ttm_tt *ttm)

@@ -156,7 +380,8 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo, bool clear, struct ttm_resource *dst_mem, struct ttm_tt *dst_ttm,

• 			     struct sg_table *dst_st)
  

• 			     struct sg_table *dst_st,
  

• 			     struct dma_fence *dep)
  

  { struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915), bdev);

@@ -180,7 +405,7 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo, return ERR_PTR(-EINVAL);

intel_engine_pm_get(i915->gt.migrate.context->engine);

• ret = intel_context_migrate_clear(i915->gt.migrate.context, NULL,
  

• ret = intel_context_migrate_clear(i915->gt.migrate.context, dep,
  			  dst_st->sgl, dst_level,
  			  i915_ttm_gtt_binds_lmem(dst_mem),
  			  0, &rq);
  

@@ -194,7 +419,7 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo, src_level = i915_ttm_cache_level(i915, bo->resource, src_ttm); intel_engine_pm_get(i915->gt.migrate.context->engine); ret = intel_context_migrate_copy(i915->gt.migrate.context,

• 				 NULL, src_rsgt->table.sgl,
  

• 				 dep, src_rsgt->table.sgl,
  			 src_level,
  			 i915_ttm_gtt_binds_lmem(bo->resource),
  			 dst_st->sgl, dst_level,
  

@@ -378,10 +603,11 @@ i915_ttm_memcpy_work_arm(struct i915_ttm_memcpy_work *work, return &work->fence; }

-static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,

• 	    struct ttm_resource *dst_mem,
  

• 	    struct ttm_tt *dst_ttm,
  

• 	    struct i915_refct_sgt *dst_rsgt, bool allow_accel)
  

+static struct dma_fence * +__i915_ttm_move(struct ttm_buffer_object *bo, bool clear,

• struct ttm_resource *dst_mem, struct ttm_tt *dst_ttm,
  

• struct i915_refct_sgt *dst_rsgt, bool allow_accel,
  

• struct dma_fence *move_dep)
  

  { struct i915_ttm_memcpy_work *copy_work = NULL; struct i915_ttm_memcpy_arg _arg, *arg = &_arg;

@@ -389,7 +615,7 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,

if (allow_accel) { fence = i915_ttm_accel_move(bo, clear, dst_mem, dst_ttm,

• 			    &dst_rsgt->table);
  

• 			    &dst_rsgt->table, move_dep);
  
  

  /*

  • We only need to intercept the error when moving to lmem.

@@ -423,6 +649,11 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,

if (!IS_ERR(fence))
	goto out;

• } else if (move_dep) {

• int err = dma_fence_wait(move_dep, true);
  

• if (err)
  

• 	return ERR_PTR(err);
  

  }

  /* Error intercept failed or no accelerated migration to start with */

@@ -433,16 +664,35 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear, i915_ttm_memcpy_release(arg); kfree(copy_work);

• return;

• return NULL; out:

• /* Sync here for now, forward the fence to caller when fully async. */
• if (fence) {

• dma_fence_wait(fence, false);
  

• dma_fence_put(fence);
  

• } else if (copy_work) {

• if (!fence && copy_work) { i915_ttm_memcpy_release(arg); kfree(copy_work); }
• return fence;

+}

+static struct dma_fence *prev_fence(struct ttm_buffer_object *bo,

• 		    struct ttm_operation_ctx *ctx)
  

+{

• struct i915_deps deps;

• int ret;

• /*

• * Instead of trying hard with GFP_KERNEL to allocate memory,
  

• * the dependency collection will just sync if it doesn't
  

• * succeed.
  

• */
  

• i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);

• ret = i915_deps_add_dependency(&deps, bo->moving, ctx);

• if (!ret)

• ret = i915_deps_add_resv(&deps, bo->base.resv, false, false, ctx);
  

• if (ret)

• return ERR_PTR(ret);
  

• return i915_deps_to_fence(&deps, ctx); }

  /**

@@ -462,16 +712,12 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict, struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo); struct ttm_resource_manager *dst_man = ttm_manager_type(bo->bdev, dst_mem->mem_type);

• struct dma_fence *migration_fence = NULL; struct ttm_tt *ttm = bo->ttm; struct i915_refct_sgt *dst_rsgt; bool clear; int ret;

• /* Sync for now. We could do the actual copy async. */
• ret = ttm_bo_wait_ctx(bo, ctx);
• if (ret)

• return ret;
  

• ret = i915_ttm_move_notify(bo); if (ret) return ret;

@@ -494,10 +740,37 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict, return PTR_ERR(dst_rsgt);

clear = !i915_ttm_cpu_maps_iomem(bo->resource) && (!ttm || !ttm_tt_is_populated(ttm));

• if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC)))

• __i915_ttm_move(bo, clear, dst_mem, bo->ttm, dst_rsgt, true);
  

• if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC))) {

• struct dma_fence *dep = prev_fence(bo, ctx);
  

• if (IS_ERR(dep)) {
  

• 	i915_refct_sgt_put(dst_rsgt);
  

• 	return PTR_ERR(dep);
  

• }
  

• migration_fence = __i915_ttm_move(bo, clear, dst_mem, bo->ttm,
  

• 				  dst_rsgt, true, dep);
  

• dma_fence_put(dep);
  

• }
• /* We can possibly get an -ERESTARTSYS here */
• if (IS_ERR(migration_fence)) {

• i915_refct_sgt_put(dst_rsgt);
  

• return PTR_ERR(migration_fence);
  

• }
• if (migration_fence) {

• ret = ttm_bo_move_accel_cleanup(bo, migration_fence, evict,
  

• 				true, dst_mem);
  

• if (ret) {
  

• 	dma_fence_wait(migration_fence, false);
  

• 	ttm_bo_move_sync_cleanup(bo, dst_mem);
  

• }
  

• dma_fence_put(migration_fence);
  

• } else {

• ttm_bo_move_sync_cleanup(bo, dst_mem);
  

• }

• ttm_bo_move_sync_cleanup(bo, dst_mem); i915_ttm_adjust_domains_after_move(obj); i915_ttm_free_cached_io_rsgt(obj);

@@ -538,6 +811,7 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst, .interruptible = intr, }; struct i915_refct_sgt *dst_rsgt;

• struct dma_fence *copy_fence; int ret;

  assert_object_held(dst);

@@ -553,10 +827,17 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst, return ret;

dst_rsgt = i915_ttm_resource_get_st(dst, dst_bo->resource);

• __i915_ttm_move(src_bo, false, dst_bo->resource, dst_bo->ttm,

• 	dst_rsgt, allow_accel);
  

• copy_fence = __i915_ttm_move(src_bo, false, dst_bo->resource,

• 		     dst_bo->ttm, dst_rsgt, allow_accel, NULL);
  
  

  i915_refct_sgt_put(dst_rsgt);

• if (IS_ERR(copy_fence))

• return PTR_ERR(copy_fence);
  

• if (copy_fence) {

• dma_fence_wait(copy_fence, false);
  

• dma_fence_put(copy_fence);
  

• }

  return 0; }

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c b/drivers/gpu/drm/i915/gem/i915_gem_wait.c index f909aaa09d9c..bae65796a6cc 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c @@ -306,6 +306,6 @@ int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj, unsigned int flags) { might_sleep();

• /* NOP for now. */
• return 0;

• return i915_gem_object_wait_moving_fence(obj, !!(flags & I915_WAIT_INTERRUPTIBLE)); }

Hi, Matthew

Finally got some time to look at this more in-depth, please see below.

On Mon, 2021-11-15 at 17:16 +0000, Matthew Auld wrote:

On 14/11/2021 11:12, Thomas Hellström wrote:

...

Don't wait sync while migrating, but rather make the GPU blit await the dependencies and add a moving fence to the object.

This also enables asynchronous VRAM management in that on eviction, rather than waiting for the moving fence to expire before freeing VRAM, it is freed immediately and the fence is stored with the VRAM manager and handed out to newly allocated objects to await before clears and swapins, or for kernel objects before setting up gpu vmas or mapping.

To collect dependencies before migrating, add a set of utilities that coalesce these to a single dma_fence.

What is still missing for fully asynchronous operation is asynchronous vma unbinding, which is still to be implemented.

This commit substantially reduces execution time in the gem_lmem_swapping test.

v2:

• Make a couple of functions static.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c      |  10 +   drivers/gpu/drm/i915/gem/i915_gem_ttm.h      |   2 +-   drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 329 +++++++++++++++++--   drivers/gpu/drm/i915/gem/i915_gem_wait.c     |   4 +-   4 files changed, 318 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index a1df49378a0f..111a4282d779 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -326,6 +326,9 @@ static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,   {         struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);   +       if (!obj) +               return false;

/*          * EXTERNAL objects should never be swapped out by TTM, instead we need          * to handle that ourselves. TTM will already skip such objects for us, @@ -448,6 +451,10 @@ static int i915_ttm_shrinker_release_pages(struct drm_i915_gem_object *obj,         if (bo->ttm->page_flags & TTM_TT_FLAG_SWAPPED)                 return 0;   +       ret = ttm_bo_wait_ctx(bo, &ctx); +       if (ret) +               return ret;

Why do we need this? Also not needed for the above purge case?

This is for bos with an on-going async move to system. The intel_migrate code doesn't set up vmas, so unbinding doesn't necessarily idle. The purge code currently idles in TTM, but in both cases we should probably add another argument to shrinker_release_pages() and move this wait before purge to return - EBUSY unless we have SHRINK_ACTIVE.

...

bo->ttm->page_flags |= TTM_TT_FLAG_SWAPPED;         ret = ttm_bo_validate(bo, &place, &ctx);         if (ret) { @@ -549,6 +556,9 @@ static void i915_ttm_swap_notify(struct ttm_buffer_object *bo)         struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);         int ret = i915_ttm_move_notify(bo);   +       if (!obj) +               return;

It looks like the i915_ttm_move_notify(bo) already dereferenced the GEM bo. Or did something in there maybe nuke it?

...

GEM_WARN_ON(ret);         GEM_WARN_ON(obj->ttm.cached_io_rsgt);         if (!ret && obj->mm.madv != I915_MADV_WILLNEED) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h index 82cdabb542be..9d698ad00853 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h @@ -37,7 +37,7 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo);   static inline struct drm_i915_gem_object *   i915_ttm_to_gem(struct ttm_buffer_object *bo)   { -       if (GEM_WARN_ON(bo->destroy != i915_ttm_bo_destroy)) +       if (bo->destroy != i915_ttm_bo_destroy)                 return NULL;

So this would indicate a "ghost" object, or is this something else? How scared should we be with this, like with the above checking for NULL GEM object state? In general do you know where we need the above checking?

Yeah, these are ghost objects and this is a major flaw in TTM in that some callbacks are per device and not per object. Should have been fixed long ago :/. For the ttm_tt callbacks, obj might be NULL but we must still be able to cope with that. For other callbacks we should ignore the ghost objects. I'll do a second audit here.

...

return container_of(bo, struct drm_i915_gem_object, __do_not_access); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c index f35b386c56ca..ae2c49fc3500 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c @@ -3,6 +3,8 @@    * Copyright © 2021 Intel Corporation    */   +#include <linux/dma-fence-array.h>

#include <drm/ttm/ttm_bo_driver.h>     #include "i915_drv.h" @@ -41,6 +43,228 @@ void i915_ttm_migrate_set_failure_modes(bool gpu_migration,   }   #endif   +/**

• • DOC: Set of utilities to dynamically collect dependencies and
• • eventually coalesce them into a single fence which is fed into
• • the migration code. That single fence is, in the case of

dependencies

• • from multiple contexts, a struct dma_fence_array, since the
• • i915 request code can break that up and await the individual
• • fences.

this? IIUC it looks like TTM expects single context/timeline for pipelined move, like with that dma_fence_is_later() check in can link to here?

Yes, currently we only have a single migration fence from the migration code so we don't need this for pipelined moves yet. But with async unbinding we do, and then we'd have to coalesce the unbind fences together with the migration fence (We can allow reading from a bo while migrating it) and then feed it to the pipelined move cleanup after attaching it to a timeline, (using dma_fence_chain I guess).

...

• • While collecting the individual dependencies, we store the

refcounted

• • struct dma_fence pointers in a realloc-type-managed pointer

array, since

• • that can be easily fed into a dma_fence_array. Other options

are

• • available, like for example an xarray for similarity with

drm/sched.

• • Can be changed easily if needed.
• • We might want to break this out into a separate file as a

utility.

• */

+#define I915_DEPS_MIN_ALLOC_CHUNK 8U

+/**

• • struct i915_deps - Collect dependencies into a single dma-fence
• • @single: Storage for pointer if the collection is a single

fence.

• • @fence: Allocated array of fence pointers if more than a single

fence;

• • otherwise points to the address of @single.
• • @num_deps: Current number of dependency fences.
• • @fences_size: Size of the @fences array in number of pointers.
• • @gfp: Allocation mode.
• */

+struct i915_deps { +       struct dma_fence *single; +       struct dma_fence **fences; +       unsigned int num_deps; +       unsigned int fences_size; +       gfp_t gfp; +};

+static void i915_deps_reset_fences(struct i915_deps *deps) +{ +       if (deps->fences != &deps->single) +               kfree(deps->fences); +       deps->num_deps = 0; +       deps->fences_size = 1; +       deps->fences = &deps->single; +}

+static void i915_deps_init(struct i915_deps *deps, gfp_t gfp) +{ +       deps->fences = NULL; +       deps->gfp = gfp; +       i915_deps_reset_fences(deps); +}

+static void i915_deps_fini(struct i915_deps *deps) +{ +       unsigned int i;

+       for (i = 0; i < deps->num_deps; ++i) +               dma_fence_put(deps->fences[i]);

+       if (deps->fences != &deps->single) +               kfree(deps->fences); +}

+static int i915_deps_grow(struct i915_deps *deps, struct dma_fence *fence, +                         const struct ttm_operation_ctx *ctx) +{ +       int ret;

+       if (deps->num_deps >= deps->fences_size) { +               unsigned int new_size = 2 * deps->fences_size; +               struct dma_fence **new_fences;

+               new_size = max(new_size, I915_DEPS_MIN_ALLOC_CHUNK); +               new_fences = kmalloc_array(new_size, sizeof(*new_fences), deps->gfp); +               if (!new_fences) +                       goto sync;

+               memcpy(new_fences, deps->fences, +                      deps->fences_size * sizeof(*new_fences)); +               swap(new_fences, deps->fences); +               if (new_fences != &deps->single) +                       kfree(new_fences); +               deps->fences_size = new_size; +       } +       deps->fences[deps->num_deps++] = dma_fence_get(fence); +       return 0;

+sync: +       if (ctx->no_wait_gpu) { +               ret = -EBUSY; +               goto unref; +       }

+       ret = dma_fence_wait(fence, ctx->interruptible); +       if (ret) +               goto unref;

+       ret = fence->error; +       if (ret) +               goto unref;

+       return 0;

+unref: +       i915_deps_fini(deps); +       return ret; +}

+static int i915_deps_sync(struct i915_deps *deps, +                         const struct ttm_operation_ctx *ctx) +{ +       unsigned int i; +       int ret = 0; +       struct dma_fence **fences = deps->fences;

Nit: Christmas tree.

Will fix.

...

+       for (i = 0; i < deps->num_deps; ++i, ++fences) { +               if (ctx->no_wait_gpu) { +                       ret = -EBUSY; +                       goto unref; +               }

+               ret = dma_fence_wait(*fences, ctx->interruptible); +               if (ret) +                       goto unref;

+               ret = (*fences)->error; +               if (ret) +                       goto unref; +       }

+       i915_deps_fini(deps); +       return 0;

+unref: +       i915_deps_fini(deps); +       return ret; +}

+static int i915_deps_add_dependency(struct i915_deps *deps, +                                   struct dma_fence *fence, +                                   const struct ttm_operation_ctx *ctx) +{ +       unsigned int i; +       int ret;

+       if (!fence) +               return 0;

+       if (dma_fence_is_signaled(fence)) { +               ret = fence->error; +               if (ret) +                       i915_deps_fini(deps); +               return ret; +       }

+       for (i = 0; i < deps->num_deps; ++i) { +               struct dma_fence *entry = deps->fences[i];

+               if (!entry->context || entry->context != fence-

...

context)

+                       continue;

+               if (dma_fence_is_later(fence, entry)) { +                       dma_fence_put(entry); +                       deps->fences[i] = dma_fence_get(fence); +               }

+               return 0; +       }

+       return i915_deps_grow(deps, fence, ctx); +}

+static struct dma_fence *i915_deps_to_fence(struct i915_deps *deps, +                                           const struct ttm_operation_ctx *ctx) +{ +       struct dma_fence_array *array;

+       if (deps->num_deps == 0) +               return NULL;

+       if (deps->num_deps == 1) { +               deps->num_deps = 0; +               return deps->fences[0]; +       }

+       /* +        * TODO: Alter the allocation mode here to not try too hard to +        * make things async. +        */ +       array = dma_fence_array_create(deps->num_deps, deps-

...

fences, 0, 0,

+                                      false); +       if (!array) +               return ERR_PTR(i915_deps_sync(deps, ctx));

+       deps->fences = NULL; +       i915_deps_reset_fences(deps);

+       return &array->base; +}

+static int i915_deps_add_resv(struct i915_deps *deps, struct dma_resv *resv, +                             bool all, const bool no_excl, +                             const struct ttm_operation_ctx *ctx) +{ +       struct dma_resv_iter iter; +       struct dma_fence *fence;

+       dma_resv_assert_held(resv); +       dma_resv_for_each_fence(&iter, resv, all, fence) { +               int ret;

+               if (no_excl && !iter.index) +                       continue;

+               ret = i915_deps_add_dependency(deps, fence, ctx); +               if (ret) +                       return ret; +       }

+       return 0; +}

static enum i915_cache_level   i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,                      struct ttm_tt *ttm) @@ -156,7 +380,8 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo,                                              bool clear,                                              struct ttm_resource *dst_mem,                                              struct ttm_tt *dst_ttm, -                                            struct sg_table *dst_st) +                                            struct sg_table *dst_st, +                                            struct dma_fence *dep)   {         struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915),                                                      bdev); @@ -180,7 +405,7 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo,                         return ERR_PTR(-EINVAL);                   intel_engine_pm_get(i915->gt.migrate.context-

...

engine);

-               ret = intel_context_migrate_clear(i915-

...

gt.migrate.context, NULL,

+               ret = intel_context_migrate_clear(i915-

...

gt.migrate.context, dep,

dst_st->sgl, dst_level,                                                   i915_ttm_gtt_binds_lmem(dst_mem),                                                   0, &rq); @@ -194,7 +419,7 @@ static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo,                 src_level = i915_ttm_cache_level(i915, bo-

...

resource, src_ttm);

intel_engine_pm_get(i915->gt.migrate.context-

...

engine);

ret = intel_context_migrate_copy(i915-

...

gt.migrate.context,

-                                                NULL, src_rsgt-

...

table.sgl,

+                                                dep, src_rsgt-

...

table.sgl,

src_level,                                                  i915_ttm_gtt_binds_lmem(bo->resource),                                                  dst_st->sgl, dst_level, @@ -378,10 +603,11 @@ i915_ttm_memcpy_work_arm(struct i915_ttm_memcpy_work *work,         return &work->fence;   }   -static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear, -                           struct ttm_resource *dst_mem, -                           struct ttm_tt *dst_ttm, -                           struct i915_refct_sgt *dst_rsgt, bool allow_accel) +static struct dma_fence * +__i915_ttm_move(struct ttm_buffer_object *bo, bool clear, +               struct ttm_resource *dst_mem, struct ttm_tt *dst_ttm, +               struct i915_refct_sgt *dst_rsgt, bool allow_accel, +               struct dma_fence *move_dep)   {         struct i915_ttm_memcpy_work *copy_work = NULL;         struct i915_ttm_memcpy_arg _arg, *arg = &_arg; @@ -389,7 +615,7 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,           if (allow_accel) {                 fence = i915_ttm_accel_move(bo, clear, dst_mem, dst_ttm, -                                           &dst_rsgt->table); +                                           &dst_rsgt->table, move_dep);                   /*                  * We only need to intercept the error when moving to lmem. @@ -423,6 +649,11 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,                   if (!IS_ERR(fence))                         goto out; +       } else if (move_dep) { +               int err = dma_fence_wait(move_dep, true);

+               if (err) +                       return ERR_PTR(err);         }           /* Error intercept failed or no accelerated migration to start with */ @@ -433,16 +664,35 @@ static void __i915_ttm_move(struct ttm_buffer_object *bo, bool clear,         i915_ttm_memcpy_release(arg);         kfree(copy_work);   -       return; +       return NULL;   out: -       /* Sync here for now, forward the fence to caller when fully async. */ -       if (fence) { -               dma_fence_wait(fence, false); -               dma_fence_put(fence); -       } else if (copy_work) { +       if (!fence && copy_work) {                 i915_ttm_memcpy_release(arg);                 kfree(copy_work);         }

+       return fence; +}

+static struct dma_fence *prev_fence(struct ttm_buffer_object *bo, +                                   struct ttm_operation_ctx *ctx) +{ +       struct i915_deps deps; +       int ret;

+       /* +        * Instead of trying hard with GFP_KERNEL to allocate memory, +        * the dependency collection will just sync if it doesn't +        * succeed. +        */ +       i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); +       ret = i915_deps_add_dependency(&deps, bo->moving, ctx); +       if (!ret) +               ret = i915_deps_add_resv(&deps, bo->base.resv, false, false, ctx); +       if (ret) +               return ERR_PTR(ret);

+       return i915_deps_to_fence(&deps, ctx);   }     /** @@ -462,16 +712,12 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,         struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);         struct ttm_resource_manager *dst_man =                 ttm_manager_type(bo->bdev, dst_mem->mem_type); +       struct dma_fence *migration_fence = NULL;         struct ttm_tt *ttm = bo->ttm;         struct i915_refct_sgt *dst_rsgt;         bool clear;         int ret;   -       /* Sync for now. We could do the actual copy async. */ -       ret = ttm_bo_wait_ctx(bo, ctx); -       if (ret) -               return ret;

ret = i915_ttm_move_notify(bo);         if (ret)                 return ret; @@ -494,10 +740,37 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,                 return PTR_ERR(dst_rsgt);           clear = !i915_ttm_cpu_maps_iomem(bo->resource) && (!ttm || !ttm_tt_is_populated(ttm)); -       if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC))) -               __i915_ttm_move(bo, clear, dst_mem, bo->ttm, dst_rsgt, true); +       if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC))) { +               struct dma_fence *dep = prev_fence(bo, ctx);

+               if (IS_ERR(dep)) { +                       i915_refct_sgt_put(dst_rsgt); +                       return PTR_ERR(dep); +               }

+               migration_fence = __i915_ttm_move(bo, clear, dst_mem, bo->ttm, +                                                 dst_rsgt, true, dep); +               dma_fence_put(dep); +       }

+       /* We can possibly get an -ERESTARTSYS here */ +       if (IS_ERR(migration_fence)) { +               i915_refct_sgt_put(dst_rsgt); +               return PTR_ERR(migration_fence); +       }

+       if (migration_fence) { +               ret = ttm_bo_move_accel_cleanup(bo, migration_fence, evict, +                                               true, dst_mem); +               if (ret) { +                       dma_fence_wait(migration_fence, false); +                       ttm_bo_move_sync_cleanup(bo, dst_mem); +               } +               dma_fence_put(migration_fence); +       } else { +               ttm_bo_move_sync_cleanup(bo, dst_mem); +       }   -       ttm_bo_move_sync_cleanup(bo, dst_mem);         i915_ttm_adjust_domains_after_move(obj);         i915_ttm_free_cached_io_rsgt(obj);   @@ -538,6 +811,7 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,                 .interruptible = intr,         };         struct i915_refct_sgt *dst_rsgt; +       struct dma_fence *copy_fence;         int ret;           assert_object_held(dst); @@ -553,10 +827,17 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,                 return ret;           dst_rsgt = i915_ttm_resource_get_st(dst, dst_bo->resource); -       __i915_ttm_move(src_bo, false, dst_bo->resource, dst_bo-

...

ttm,

-                       dst_rsgt, allow_accel); +       copy_fence = __i915_ttm_move(src_bo, false, dst_bo-

...

resource,

+                                    dst_bo->ttm, dst_rsgt, allow_accel, NULL);           i915_refct_sgt_put(dst_rsgt); +       if (IS_ERR(copy_fence)) +               return PTR_ERR(copy_fence);

+       if (copy_fence) { +               dma_fence_wait(copy_fence, false); +               dma_fence_put(copy_fence); +       }           return 0;   } diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c b/drivers/gpu/drm/i915/gem/i915_gem_wait.c index f909aaa09d9c..bae65796a6cc 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c @@ -306,6 +306,6 @@ int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj,                                    unsigned int flags)   {         might_sleep(); -       /* NOP for now. */ -       return 0;

+       return i915_gem_object_wait_moving_fence(obj, !!(flags & I915_WAIT_INTERRUPTIBLE));   }