v1: AMD is building a system architecture for the Frontier supercomputer with a coherent interconnect between CPUs and GPUs. This hardware architecture allows the CPUs to coherently access GPU device memory. We have hardware in our labs and we are working with our partner HPE on the BIOS, firmware and software for delivery to the DOE.
The system BIOS advertises the GPU device memory (aka VRAM) as SPM (special purpose memory) in the UEFI system address map. The amdgpu driver looks it up with lookup_resource and registers it with devmap as MEMORY_DEVICE_GENERIC using devm_memremap_pages.
Now we're trying to migrate data to and from that memory using the migrate_vma_* helpers so we can support page-based migration in our unified memory allocations, while also supporting CPU access to those pages.
This patch series makes a few changes to make MEMORY_DEVICE_GENERIC pages behave correctly in the migrate_vma_* helpers. We are looking for feedback about this approach. If we're close, what's needed to make our patches acceptable upstream? If we're not close, any suggestions how else to achieve what we are trying to do (i.e. page migration and coherent CPU access to VRAM)?
This work is based on HMM and our SVM memory manager that was recently upstreamed to Dave Airlie's drm-next branch https://cgit.freedesktop.org/drm/drm/log/?h=drm-next On top of that we did some rework of our VRAM management for migrations to remove some incorrect assumptions, allow partially successful migrations and GPU memory mappings that mix pages in VRAM and system memory. https://lore.kernel.org/dri-devel/20210527205606.2660-6-Felix.Kuehling@amd.c...
v2: This patch series version has merged "[RFC PATCH v3 0/2] mm: remove extra ZONE_DEVICE struct page refcount" patch series made by Ralph Campbell. It also applies at the top of these series, our changes to support device generic type in migration_vma helpers. This has been tested in systems with device memory that has coherent access by CPU.
Also addresses the following feedback made in v1: - Isolate in one patch kernel/resource.c modification, based on Christoph's feedback. - Add helpers check for generic and private type to avoid duplicated long lines.
v3: - Include cover letter from v1. - Rename dax_layout_is_idle_page func to dax_page_unused in patch ext4/xfs: add page refcount helper.
v4: - Add support for zone device generic type in lib/test_hmm and tool/testing/selftest/vm/hmm-tests. - Add missing page refcount helper to fuse/dax.c. This was included in one of Ralph Campbell's patches.
v5: - Cosmetic changes on patches 3, 5 and 13 - A bug was found while running one of the xfstest (generic/413) used to validate fs_dax device type. This was first introduced by patch: "mm: remove extra ZONE_DEVICE struct page refcount" whic is part of these patch series. The bug was showed as WARNING message at try_grab_page function call, due to a page refcounter equal to zero. Part of "mm: remove extra ZONE_DEVICE struct page refcount" changes, was to initialize page refcounter to zero. Therefore, a special condition was added to try_grab_page on this v5, were it checks for device zone pages too. It is included in the same patch.
This is how mm changes from these patch series have been validated: - hmm-tests were run using device private and device generic types. This last, just added in these patch series. efi_fake_mem was used to mimic SPM memory for device generic. - xfstests tool was used to validate fs-dax device type and page refcounter changes. DAX configuration was used along with emulated Persisten Memory set as memmap=4G!4G memmap=4G!9G. xfstests were run from ext4 and generic lists. Some of them, did not run due to limitations in configuration. Ex. test not supporting specific file system or DAX mode. Only three tests failed, generic/356/357 and ext4/049. However, these failures were consistent before and after applying these patch series. xfstest configuration: TEST_DEV=/dev/pmem0 TEST_DIR=/mnt/ram0 SCRATCH_DEV=/dev/pmem1 SCRATCH_MNT=/mnt/ram1 TEST_FS_MOUNT_OPTS="-o dax" EXT_MOUNT_OPTIONS="-o dax" MKFS_OPTIONS="-b4096" xfstest passed list: Ext4: 001,003,005,021,022,023,025,026,030,031,032,036,037,038,042,043,044,271,306 Generic: 1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,20,21,22,23,24,25,28,29,30,31,32,33,35,37, 50,52,53,58,60,61,62,63,64,67,69,70,71,75,76,78,79,80,82,84,86,87,88,91,92,94, 96,97,98,99,103,105,112,113,114,117,120,124,126,129,130,131,135,141,169,184, 198,207,210,211,212,213,214,215,221,223,225,228,236,237,240,244,245,246,247, 248,249,255,257,258,263,277,286,294,306,307,308,309,313,315,316,318,319,337, 346,360,361,371,375,377,379,380,383,384,385,386,389,391,392,393,394,400,401, 403,404,406,409,410,411,412,413,417,420,422,423,424,425,426,427,428
v6: - These patch series was rebased on amd-staging-drm-next, which in turn is based on v5.13: https://gitlab.freedesktop.org/agd5f/linux/-/tree/amd-staging-drm-next - Handle null pointers in dmirror_allocate_chunk at test_hmm.c - Here's a link to the repo including these patch series: https://github.com/RadeonOpenCompute/ROCK-Kernel-Driver/tree/alexsierrag/dev...
- CONFIGS required to run hmm-tests and xfstest with no special Hardware. For hmm-tests: CONFIG_EFI_FAKE_MEMMAP=y CONFIG_EFI_SOFT_RESERVE=y CONFIG_TEST_HMM=m CONFIG_RUNTIME_TESTING_MENU=y
For xfstest using emulated persistant memory: CONFIG_X86_PMEM_LEGACY=y CONFIG_LIBNVDIMM=y CONFIG_BLK_DEV_PMEM=y CONFIG_FS_DAX=y CONFIG_DAX_DRIVER=y CONFIG_VIRTIO_FS=y
HMM configs for both hmm-test and xfstest: CONFIG_ZONE_DEVICE=y CONFIG_HMM_MIRROR=y CONFIG_MMU_NOTIFIER=y CONFIG_DEVICE_PRIVATE=y
- Kernel parameters to run hmm-tests and xfstests. These tests require to either emulate persistent memory (EPM) for xfstests or fake special memory purpose (FSPM) for hmm-tests device generic type configuration. This is achieved by using system memory for both purposes. The idea is to reserve ranges of physical address by passing specific kernel parameters. Make sure your kernel has built with the proper CONFIGS mentioned above. Once you reserve memory ranges through these two mechanisms, they cannot be used by the kernel as regular system memory. Until these kernel parameters are removed. Both mechanisms use similar parameters to define physical address and size. FSPM, however, uses a third field which is the attribute value. Here’s the syntax for both: FSPM: efi_fake_mem= nn[KMG]@ss[KMG]:aa EPM: memmap=nn[KMG]!ss[KMG] 'nn' defines the size (in GB) of memory reserved 'mm' physical/usable start address. This can be taken from BIOS-e820 mem table 'aa' specify attribute. SPM attribute is EFI_MEMORY_SP(0x40000) [KMG]: refers to kilo, mega, giga To find an available memory region address, you could look into BIOS-e820 mem table. Usually this is printed at kernel boot (dmesg). At this table, make sure you choose ranges marked as 'usable' and has at least the same or more range size as your desired reservation. Ex. Range below has a size of 13GB, from a total of 16GB of system memory. [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000044eafffff] usable
In our testing, we require two ranges of 4GB each for xfstests. And two more of 1GB each for hmm-tests. Total of 10GB.
Based on range above we set these two kernel parameters as follows: EPM: memmap=4G!4G memmap=4G!9G FSPM: efi_fake_mem=1G@0x200000000:0x40000,1G@0x340000000:0x40000 We alternate one EPM reserve (4GB) and one FSPM (1GB). Starting @4GB address. These kernel parameters can be passed by editing grub file. Under "/etc/default/grub". GRUB_CMDLINE_LINUX="memmap=4G!4G memmap=4G!9G efi_fake_mem=1G@0x200000000:0x40000,1G@0x340000000:0x40000" Once you have modified this file, don’t forget to update the grub. $sudo update-grub
After booting with these parameters applied, you should see the new ranges defined at the "extended physical RAM map" table. This is printed at boot: reserve setup_data: [mem 0x0000000100000000-0x00000001ffffffff] persistent (type 12)
reserve setup_data: [mem 0x0000000200000000-0x000000023fffffff] soft reserved
reserve setup_data: [mem 0x0000000240000000-0x000000033fffffff] persistent (type 12)
reserve setup_data: [mem 0x0000000340000000-0x000000037fffffff] soft reserved
As you see, EPM ranges are now labeled as Persistent (type 12) and FSPM ranges as soft reserved.
- Setting and running hmm-tests These tests can now be run either with device private or device generic types. This last, by setting Special Purpose Memory. To manually run them, on your kernel directory go to: $cd tools/testing/selftests/vm/
To run device private, enter: $sudo ./test_hmm.sh smoke
To run device generic, you must pass the physical start addresses for both SP regions. In this example, these can be taken from above’s table labeled with "soft reserved": $sudo ./test_hmm.sh smoke 0x200000000 0x340000000
The same hmm-tests are executed for both device types.
- Setting and running xfstest Clone xfstests-dev repo $git clone git://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git $cd xfstests-dev $make $sudo make install
On xfstests-dev directory, create a local.config file with the following information: TEST_DEV=/dev/pmem0 TEST_DIR=/mnt/ram0 SCRATCH_DEV=/dev/pmem1 SCRATCH_MNT=/mnt/ram1 TEST_FS_MOUNT_OPTS="-o dax" EXT_MOUNT_OPTIONS="-o dax" MKFS_OPTIONS="-b4096"
Create mounting directories: $sudo mkdir /mnt/ram0 $sudo mkdir /mnt/ram1
Everytime you boot, you need to create ext4 file system for the emulated persistent memory partitions. $sudo mkfs.ext4 /dev/pmem0 $sudo mkfs.ext4 /dev/pmem1
To run the tests: $sudo ./check -g quick
Alex Sierra (11): kernel: resource: lookup_resource as exported symbol drm/amdkfd: add SPM support for SVM drm/amdkfd: generic type as sys mem on migration to ram include/linux/mm.h: helpers to check zone device generic type mm: add generic type support to migrate_vma helpers mm: call pgmap->ops->page_free for DEVICE_GENERIC pages lib: test_hmm add ioctl to get zone device type lib: test_hmm add module param for zone device type lib: add support for device generic type in test_hmm tools: update hmm-test to support device generic type tools: update test_hmm script to support SP config
Ralph Campbell (2): ext4/xfs: add page refcount helper mm: remove extra ZONE_DEVICE struct page refcount
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 22 ++- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 8 +- fs/ext4/inode.c | 5 +- fs/fuse/dax.c | 4 +- fs/xfs/xfs_file.c | 4 +- include/linux/dax.h | 10 + include/linux/memremap.h | 7 +- include/linux/mm.h | 21 +- kernel/resource.c | 1 + lib/test_hmm.c | 237 +++++++++++++++-------- lib/test_hmm_uapi.h | 16 ++ mm/internal.h | 8 + mm/memremap.c | 69 ++----- mm/migrate.c | 23 ++- mm/page_alloc.c | 3 + mm/swap.c | 45 +---- tools/testing/selftests/vm/hmm-tests.c | 142 ++++++++++++-- tools/testing/selftests/vm/test_hmm.sh | 20 +- 20 files changed, 411 insertions(+), 238 deletions(-)
From: Ralph Campbell rcampbell@nvidia.com
There are several places where ZONE_DEVICE struct pages assume a reference count == 1 means the page is idle and free. Instead of open coding this, add a helper function to hide this detail.
v3: [AS]: rename dax_layout_is_idle_page func to dax_page_unused
v4: [AS]: This ref count functionality was missing on fuse/dax.c.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com --- fs/dax.c | 4 ++-- fs/ext4/inode.c | 5 +---- fs/fuse/dax.c | 4 +--- fs/xfs/xfs_file.c | 4 +--- include/linux/dax.h | 10 ++++++++++ 5 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c index 62352cbcf0f4..c387d09e3e5a 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -369,7 +369,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping, for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn);
- WARN_ON_ONCE(trunc && page_ref_count(page) > 1); + WARN_ON_ONCE(trunc && !dax_page_unused(page)); WARN_ON_ONCE(page->mapping && page->mapping != mapping); page->mapping = NULL; page->index = 0; @@ -383,7 +383,7 @@ static struct page *dax_busy_page(void *entry) for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn);
- if (page_ref_count(page) > 1) + if (!dax_page_unused(page)) return page; } return NULL; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index fe6045a46599..05ffe6875cb1 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3971,10 +3971,7 @@ int ext4_break_layouts(struct inode *inode) if (!page) return 0;
- error = ___wait_var_event(&page->_refcount, - atomic_read(&page->_refcount) == 1, - TASK_INTERRUPTIBLE, 0, 0, - ext4_wait_dax_page(ei)); + error = dax_wait_page(ei, page, ext4_wait_dax_page); } while (error == 0);
return error; diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c index ff99ab2a3c43..2b1f190ba78a 100644 --- a/fs/fuse/dax.c +++ b/fs/fuse/dax.c @@ -677,9 +677,7 @@ static int __fuse_dax_break_layouts(struct inode *inode, bool *retry, return 0;
*retry = true; - return ___wait_var_event(&page->_refcount, - atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, - 0, 0, fuse_wait_dax_page(inode)); + return dax_wait_page(inode, page, fuse_wait_dax_page); }
/* dmap_end == 0 leads to unmapping of whole file */ diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 396ef36dcd0a..182057281086 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -840,9 +840,7 @@ xfs_break_dax_layouts( return 0;
*retry = true; - return ___wait_var_event(&page->_refcount, - atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, - 0, 0, xfs_wait_dax_page(inode)); + return dax_wait_page(inode, page, xfs_wait_dax_page); }
int diff --git a/include/linux/dax.h b/include/linux/dax.h index b52f084aa643..8b5da1d60dbc 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -243,6 +243,16 @@ static inline bool dax_mapping(struct address_space *mapping) return mapping->host && IS_DAX(mapping->host); }
+static inline bool dax_page_unused(struct page *page) +{ + return page_ref_count(page) == 1; +} + +#define dax_wait_page(_inode, _page, _wait_cb) \ + ___wait_var_event(&(_page)->_refcount, \ + dax_page_unused(_page), \ + TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode)) + #ifdef CONFIG_DEV_DAX_HMEM_DEVICES void hmem_register_device(int target_nid, struct resource *r); #else
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com --- arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c index 84e5a2dc8be5..acee67710620 100644 --- a/arch/powerpc/kvm/book3s_hv_uvmem.c +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c @@ -711,7 +711,7 @@ static struct page *kvmppc_uvmem_get_page(unsigned long gpa, struct kvm *kvm)
dpage = pfn_to_page(uvmem_pfn); dpage->zone_device_data = pvt; - get_page(dpage); + init_page_count(dpage); lock_page(dpage); return dpage; out_clear: diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c index 92987daa5e17..8bc7120e1216 100644 --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c @@ -324,7 +324,7 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm) return NULL; }
- get_page(page); + init_page_count(page); lock_page(page); return page; } diff --git a/fs/dax.c b/fs/dax.c index c387d09e3e5a..1166630b7190 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -571,14 +571,14 @@ static void *grab_mapping_entry(struct xa_state *xas,
/** * dax_layout_busy_page_range - find first pinned page in @mapping - * @mapping: address space to scan for a page with ref count > 1 + * @mapping: address space to scan for a page with ref count > 0 * @start: Starting offset. Page containing 'start' is included. * @end: End offset. Page containing 'end' is included. If 'end' is LLONG_MAX, * pages from 'start' till the end of file are included. * * DAX requires ZONE_DEVICE mapped pages. These pages are never * 'onlined' to the page allocator so they are considered idle when - * page->count == 1. A filesystem uses this interface to determine if + * page->count == 0. A filesystem uses this interface to determine if * any page in the mapping is busy, i.e. for DMA, or other * get_user_pages() usages. * diff --git a/include/linux/dax.h b/include/linux/dax.h index 8b5da1d60dbc..05fc982ce153 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -245,7 +245,7 @@ static inline bool dax_mapping(struct address_space *mapping)
static inline bool dax_page_unused(struct page *page) { - return page_ref_count(page) == 1; + return page_ref_count(page) == 0; }
#define dax_wait_page(_inode, _page, _wait_cb) \ diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 45a79da89c5f..77ff5fd0685f 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -66,9 +66,10 @@ enum memory_type {
struct dev_pagemap_ops { /* - * Called once the page refcount reaches 1. (ZONE_DEVICE pages never - * reach 0 refcount unless there is a refcount bug. This allows the - * device driver to implement its own memory management.) + * Called once the page refcount reaches 0. The reference count + * should be reset to one with init_page_count(page) before reusing + * the page. This allows the device driver to implement its own + * memory management. */ void (*page_free)(struct page *page);
diff --git a/include/linux/mm.h b/include/linux/mm.h index 8ae31622deef..d48a1f0889d1 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1218,7 +1218,7 @@ __maybe_unused struct page *try_grab_compound_head(struct page *page, int refs, static inline __must_check bool try_get_page(struct page *page) { page = compound_head(page); - if (WARN_ON_ONCE(page_ref_count(page) <= 0)) + if (WARN_ON_ONCE(page_ref_count(page) < (int)!is_zone_device_page(page))) return false; page_ref_inc(page); return true; @@ -1228,17 +1228,6 @@ static inline void put_page(struct page *page) { page = compound_head(page);
- /* - * For devmap managed pages we need to catch refcount transition from - * 2 to 1, when refcount reach one it means the page is free and we - * need to inform the device driver through callback. See - * include/linux/memremap.h and HMM for details. - */ - if (page_is_devmap_managed(page)) { - put_devmap_managed_page(page); - return; - } - if (put_page_testzero(page)) __put_page(page); } diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 80a78877bd93..6998f10350ea 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -561,7 +561,7 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice) }
dpage->zone_device_data = rpage; - get_page(dpage); + init_page_count(dpage); lock_page(dpage); return dpage;
diff --git a/mm/internal.h b/mm/internal.h index e8fdb531f887..5438cceca4b9 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -667,4 +667,12 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
void vunmap_range_noflush(unsigned long start, unsigned long end);
+#ifdef CONFIG_DEV_PAGEMAP_OPS +void free_zone_device_page(struct page *page); +#else +static inline void free_zone_device_page(struct page *page) +{ +} +#endif + #endif /* __MM_INTERNAL_H */ diff --git a/mm/memremap.c b/mm/memremap.c index 15a074ffb8d7..5aa8163fd948 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -12,6 +12,7 @@ #include <linux/types.h> #include <linux/wait_bit.h> #include <linux/xarray.h> +#include "internal.h"
static DEFINE_XARRAY(pgmap_array);
@@ -37,32 +38,6 @@ unsigned long memremap_compat_align(void) EXPORT_SYMBOL_GPL(memremap_compat_align); #endif
-#ifdef CONFIG_DEV_PAGEMAP_OPS -DEFINE_STATIC_KEY_FALSE(devmap_managed_key); -EXPORT_SYMBOL(devmap_managed_key); - -static void devmap_managed_enable_put(struct dev_pagemap *pgmap) -{ - if (pgmap->type == MEMORY_DEVICE_PRIVATE || - pgmap->type == MEMORY_DEVICE_FS_DAX) - static_branch_dec(&devmap_managed_key); -} - -static void devmap_managed_enable_get(struct dev_pagemap *pgmap) -{ - if (pgmap->type == MEMORY_DEVICE_PRIVATE || - pgmap->type == MEMORY_DEVICE_FS_DAX) - static_branch_inc(&devmap_managed_key); -} -#else -static void devmap_managed_enable_get(struct dev_pagemap *pgmap) -{ -} -static void devmap_managed_enable_put(struct dev_pagemap *pgmap) -{ -} -#endif /* CONFIG_DEV_PAGEMAP_OPS */ - static void pgmap_array_delete(struct range *range) { xa_store_range(&pgmap_array, PHYS_PFN(range->start), PHYS_PFN(range->end), @@ -102,16 +77,6 @@ static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id) return (range->start + range_len(range)) >> PAGE_SHIFT; }
-static unsigned long pfn_next(unsigned long pfn) -{ - if (pfn % 1024 == 0) - cond_resched(); - return pfn + 1; -} - -#define for_each_device_pfn(pfn, map, i) \ - for (pfn = pfn_first(map, i); pfn < pfn_end(map, i); pfn = pfn_next(pfn)) - static void dev_pagemap_kill(struct dev_pagemap *pgmap) { if (pgmap->ops && pgmap->ops->kill) @@ -167,20 +132,18 @@ static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
void memunmap_pages(struct dev_pagemap *pgmap) { - unsigned long pfn; int i;
dev_pagemap_kill(pgmap); for (i = 0; i < pgmap->nr_range; i++) - for_each_device_pfn(pfn, pgmap, i) - put_page(pfn_to_page(pfn)); + percpu_ref_put_many(pgmap->ref, pfn_end(pgmap, i) - + pfn_first(pgmap, i)); dev_pagemap_cleanup(pgmap);
for (i = 0; i < pgmap->nr_range; i++) pageunmap_range(pgmap, i);
WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n"); - devmap_managed_enable_put(pgmap); } EXPORT_SYMBOL_GPL(memunmap_pages);
@@ -382,8 +345,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid) } }
- devmap_managed_enable_get(pgmap); - /* * Clear the pgmap nr_range as it will be incremented for each * successfully processed range. This communicates how many @@ -498,16 +459,10 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, EXPORT_SYMBOL_GPL(get_dev_pagemap);
#ifdef CONFIG_DEV_PAGEMAP_OPS -void free_devmap_managed_page(struct page *page) +static void free_device_private_page(struct page *page) { - /* notify page idle for dax */ - if (!is_device_private_page(page)) { - wake_up_var(&page->_refcount); - return; - }
__ClearPageWaiters(page); - mem_cgroup_uncharge(page);
/* @@ -534,4 +489,19 @@ void free_devmap_managed_page(struct page *page) page->mapping = NULL; page->pgmap->ops->page_free(page); } + +void free_zone_device_page(struct page *page) +{ + switch (page->pgmap->type) { + case MEMORY_DEVICE_FS_DAX: + /* notify page idle */ + wake_up_var(&page->_refcount); + return; + case MEMORY_DEVICE_PRIVATE: + free_device_private_page(page); + return; + default: + return; + } +} #endif /* CONFIG_DEV_PAGEMAP_OPS */ diff --git a/mm/migrate.c b/mm/migrate.c index 41ff2c9896c4..e3a10e2a1bb3 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -350,11 +350,6 @@ static int expected_page_refs(struct address_space *mapping, struct page *page) { int expected_count = 1;
- /* - * Device private pages have an extra refcount as they are - * ZONE_DEVICE pages. - */ - expected_count += is_device_private_page(page); if (mapping) expected_count += thp_nr_pages(page) + page_has_private(page);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ef2265f86b91..1ef1f733af5b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6414,6 +6414,9 @@ void __ref memmap_init_zone_device(struct zone *zone,
__init_single_page(page, pfn, zone_idx, nid);
+ /* ZONE_DEVICE pages start with a zero reference count. */ + set_page_count(page, 0); + /* * Mark page reserved as it will need to wait for onlining * phase for it to be fully associated with a zone. diff --git a/mm/swap.c b/mm/swap.c index dfb48cf9c2c9..9e821f1951c5 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -114,12 +114,11 @@ static void __put_compound_page(struct page *page) void __put_page(struct page *page) { if (is_zone_device_page(page)) { - put_dev_pagemap(page->pgmap); - /* * The page belongs to the device that created pgmap. Do * not return it to page allocator. */ + free_zone_device_page(page); return; }
@@ -917,29 +916,18 @@ void release_pages(struct page **pages, int nr) if (is_huge_zero_page(page)) continue;
+ if (!put_page_testzero(page)) + continue; + if (is_zone_device_page(page)) { if (lruvec) { unlock_page_lruvec_irqrestore(lruvec, flags); lruvec = NULL; } - /* - * ZONE_DEVICE pages that return 'false' from - * page_is_devmap_managed() do not require special - * processing, and instead, expect a call to - * put_page_testzero(). - */ - if (page_is_devmap_managed(page)) { - put_devmap_managed_page(page); - continue; - } - if (put_page_testzero(page)) - put_dev_pagemap(page->pgmap); + free_zone_device_page(page); continue; }
- if (!put_page_testzero(page)) - continue; - if (PageCompound(page)) { if (lruvec) { unlock_page_lruvec_irqrestore(lruvec, flags); @@ -1143,26 +1131,3 @@ void __init swap_setup(void) * _really_ don't want to cluster much more */ } - -#ifdef CONFIG_DEV_PAGEMAP_OPS -void put_devmap_managed_page(struct page *page) -{ - int count; - - if (WARN_ON_ONCE(!page_is_devmap_managed(page))) - return; - - count = page_ref_dec_return(page); - - /* - * devmap page refcounts are 1-based, rather than 0-based: if - * refcount is 1, then the page is free and the refcount is - * stable because nobody holds a reference on the page. - */ - if (count == 1) - free_devmap_managed_page(page); - else if (!count) - __put_page(page); -} -EXPORT_SYMBOL(put_devmap_managed_page); -#endif
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://lore.kernel.org/linux-mm/4f6dd918-d79b-1aa7-3a4c-caa67ddc29bc@nvidia...
Did I miss something?
Am 2021-08-17 um 8:01 p.m. schrieb Ralph Campbell:
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://lore.kernel.org/linux-mm/4f6dd918-d79b-1aa7-3a4c-caa67ddc29bc@nvidia...
Did I miss something?
I think part of the response was that we did more testing. Alex added support for DEVICE_GENERIC pages to test_hmm and he ran DAX tests recommended by Theodore Tso. In that testing he ran into a WARN_ON_ONCE about a zero page refcount in try_get_page. The fix is in the latest version of patch 2. But it's already obsolete because John Hubbard is about to remove that function altogether.
I think the issues you raised were more uncertainty than known bugs. It seems the fact that you can have DAX pages with 0 refcount is a feature more than a bug.
Regards, Felix
On 8/17/21 5:35 PM, Felix Kuehling wrote:
Am 2021-08-17 um 8:01 p.m. schrieb Ralph Campbell:
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://lore.kernel.org/linux-mm/4f6dd918-d79b-1aa7-3a4c-caa67ddc29bc@nvidia...
Did I miss something?
I think part of the response was that we did more testing. Alex added support for DEVICE_GENERIC pages to test_hmm and he ran DAX tests recommended by Theodore Tso. In that testing he ran into a WARN_ON_ONCE about a zero page refcount in try_get_page. The fix is in the latest version of patch 2. But it's already obsolete because John Hubbard is about to remove that function altogether.
I think the issues you raised were more uncertainty than known bugs. It seems the fact that you can have DAX pages with 0 refcount is a feature more than a bug.
Regards, Felix
Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? In that case, mmap() of a DAX device will call insert_page() which calls get_page() which would trigger VM_BUG_ON_PAGE().
I can believe it is OK for PTE_SPECIAL page table entries to have no struct page or that MEMORY_DEVICE_GENERIC struct pages be mapped with a zero reference count using insert_pfn().
I find it hard to believe that other MM developers don't see an issue with a struct page with refcount == 0 and mapcount == 1.
I don't see where init_page_count() is being called for the MEMORY_DEVICE_GENERIC or MEMORY_DEVICE_PRIVATE struct pages the AMD driver allocates and passes to migrate_vma_setup(). Looks like svm_migrate_get_vram_page() needs to call init_page_count() instead of get_page(). (I'm looking at branch origin/alexsierrag/device_generic https://github.com/RadeonOpenCompute/ROCK-Kernel-Driver.git)
Also, what about the other places where is_device_private_page() is called? Don't they need to be updated to call is_device_page() instead? One of my goals for this patch was to remove special casing reference counts for ZONE_DEVICE pages in rmap.c, etc.
I still think this patch needs an ACK from a FS/DAX maintainer.
On 8/18/2021 2:28 PM, Ralph Campbell wrote:
On 8/17/21 5:35 PM, Felix Kuehling wrote:
Am 2021-08-17 um 8:01 p.m. schrieb Ralph Campbell:
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kerne...
Did I miss something?
I think part of the response was that we did more testing. Alex added support for DEVICE_GENERIC pages to test_hmm and he ran DAX tests recommended by Theodore Tso. In that testing he ran into a WARN_ON_ONCE about a zero page refcount in try_get_page. The fix is in the latest version of patch 2. But it's already obsolete because John Hubbard is about to remove that function altogether.
I think the issues you raised were more uncertainty than known bugs. It seems the fact that you can have DAX pages with 0 refcount is a feature more than a bug.
Regards, Felix
Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? In that case, mmap() of a DAX device will call insert_page() which calls get_page() which would trigger VM_BUG_ON_PAGE().
I can believe it is OK for PTE_SPECIAL page table entries to have no struct page or that MEMORY_DEVICE_GENERIC struct pages be mapped with a zero reference count using insert_pfn().
Hi Ralph, We have tried the DAX tests with and without CONFIG_ARCH_HAS_PTE_SPECIAL defined. Apparently none of the tests touches that condition for a DAX device. Of course, that doesn't mean it could happen.
Regards, Alex S.
I find it hard to believe that other MM developers don't see an issue with a struct page with refcount == 0 and mapcount == 1.
I don't see where init_page_count() is being called for the MEMORY_DEVICE_GENERIC or MEMORY_DEVICE_PRIVATE struct pages the AMD driver allocates and passes to migrate_vma_setup(). Looks like svm_migrate_get_vram_page() needs to call init_page_count() instead of get_page(). (I'm looking at branch origin/alexsierrag/device_generic https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com...)
Yes, you're right. My bad. Thanks for catching this up. I didn't realize I was missing to define CONFIG_DEBUG_VM on my build. Therefore this BUG was never caught. It worked after I replaced get_pages by init_page_count at svm_migrate_get_vram_page. However, I don't think this is the best way to fix it. Ideally, get_pages call should work for device pages with ref count equal to 0 too. Otherwise, we could overwrite refcounter if someone else is grabbing the page concurrently. I was thinking to add a special condition in get_pages for dev pages. This could also fix the insert_page -> get_page call from a DAX device.
Regards, Alex S.
Also, what about the other places where is_device_private_page() is called? Don't they need to be updated to call is_device_page() instead? One of my goals for this patch was to remove special casing reference counts for ZONE_DEVICE pages in rmap.c, etc.
Correct, is_device_private_page is still used in rmap, memcontrol and migrate.c files Looks like rmap and memcontrol should be replaced by is_device_page function. However, I still need test to validate this. For migrate.c is used in remove_migration_pte and migrate_vma_insert_page, however these are specific conditions for private device type Thanks for raise these questions, I think we're getting close.
Regards, Alex S.
I still think this patch needs an ACK from a FS/DAX maintainer.
Am 2021-08-19 um 2:00 p.m. schrieb Sierra Guiza, Alejandro (Alex):
On 8/18/2021 2:28 PM, Ralph Campbell wrote:
On 8/17/21 5:35 PM, Felix Kuehling wrote:
Am 2021-08-17 um 8:01 p.m. schrieb Ralph Campbell:
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://lore.kernel.org/linux-mm/4f6dd918-d79b-1aa7-3a4c-caa67ddc29bc@nvidia...
Did I miss something?
I think part of the response was that we did more testing. Alex added support for DEVICE_GENERIC pages to test_hmm and he ran DAX tests recommended by Theodore Tso. In that testing he ran into a WARN_ON_ONCE about a zero page refcount in try_get_page. The fix is in the latest version of patch 2. But it's already obsolete because John Hubbard is about to remove that function altogether.
I think the issues you raised were more uncertainty than known bugs. It seems the fact that you can have DAX pages with 0 refcount is a feature more than a bug.
Regards, Felix
Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? In that case, mmap() of a DAX device will call insert_page() which calls get_page() which would trigger VM_BUG_ON_PAGE().
I can believe it is OK for PTE_SPECIAL page table entries to have no struct page or that MEMORY_DEVICE_GENERIC struct pages be mapped with a zero reference count using insert_pfn().
Hi Ralph, We have tried the DAX tests with and without CONFIG_ARCH_HAS_PTE_SPECIAL defined. Apparently none of the tests touches that condition for a DAX device. Of course, that doesn't mean it could happen.
Regards, Alex S.
I find it hard to believe that other MM developers don't see an issue with a struct page with refcount == 0 and mapcount == 1.
I don't see where init_page_count() is being called for the MEMORY_DEVICE_GENERIC or MEMORY_DEVICE_PRIVATE struct pages the AMD driver allocates and passes to migrate_vma_setup(). Looks like svm_migrate_get_vram_page() needs to call init_page_count() instead of get_page(). (I'm looking at branch origin/alexsierrag/device_generic https://github.com/RadeonOpenCompute/ROCK-Kernel-Driver.git
Yes, you're right. My bad. Thanks for catching this up. I didn't realize I was missing to define CONFIG_DEBUG_VM on my build. Therefore this BUG was never caught. It worked after I replaced get_pages by init_page_count at svm_migrate_get_vram_page. However, I don't think this is the best way to fix it. Ideally, get_pages call should work for device pages with ref count equal to 0 too. Otherwise, we could overwrite refcounter if someone else is grabbing the page concurrently.
I think using init_page_count in svm_migrate_get_vram_page is the right answer. This is where the page first gets allocated and initialized (data migrated into it). I think nobody should have or try to take a reference to the page before that. We should probably also add a VM_BUG_ON_PAGE(page_ref_count(page) != 0) before calling init_page_count to make sure of that.
I was thinking to add a special condition in get_pages for dev pages. This could also fix the insert_page -> get_page call from a DAX device.
[+Theodore]
I got lost trying to understand how DAX counts page references and how the PTE_SPECIAL option affects that. Theodore, can you help with this? Is there an easy way to test without CONFIG_ARCH_HAS_PTE_SPECIAL on x86, or do we need to test on a CPU architecture that doesn't support this feature?
Thanks, Felix
Regards, Alex S.
Also, what about the other places where is_device_private_page() is called? Don't they need to be updated to call is_device_page() instead? One of my goals for this patch was to remove special casing reference counts for ZONE_DEVICE pages in rmap.c, etc.
Correct, is_device_private_page is still used in rmap, memcontrol and migrate.c files Looks like rmap and memcontrol should be replaced by is_device_page function. However, I still need test to validate this. For migrate.c is used in remove_migration_pte and migrate_vma_insert_page, however these are specific conditions for private device type Thanks for raise these questions, I think we're getting close.
Regards, Alex S.
I still think this patch needs an ACK from a FS/DAX maintainer.
On Thu, Aug 19, 2021 at 11:00 AM Sierra Guiza, Alejandro (Alex) alex.sierra@amd.com wrote:
On 8/18/2021 2:28 PM, Ralph Campbell wrote:
On 8/17/21 5:35 PM, Felix Kuehling wrote:
Am 2021-08-17 um 8:01 p.m. schrieb Ralph Campbell:
On 8/12/21 11:31 PM, Alex Sierra wrote:
From: Ralph Campbell rcampbell@nvidia.com
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE.
v2: AS: merged this patch in linux 5.11 version
v5: AS: add condition at try_grab_page to check for the zone device type, while page ref counter is checked less/equal to zero. In case of device zone, pages ref counter are initialized to zero.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Alex Sierra alex.sierra@amd.com
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +- drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +- fs/dax.c | 4 +- include/linux/dax.h | 2 +- include/linux/memremap.h | 7 +-- include/linux/mm.h | 13 +---- lib/test_hmm.c | 2 +- mm/internal.h | 8 +++ mm/memremap.c | 68 +++++++------------------- mm/migrate.c | 5 -- mm/page_alloc.c | 3 ++ mm/swap.c | 45 ++--------------- 12 files changed, 46 insertions(+), 115 deletions(-)
I haven't seen a response to the issues I raised back at v3 of this series. https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kerne...
Did I miss something?
I think part of the response was that we did more testing. Alex added support for DEVICE_GENERIC pages to test_hmm and he ran DAX tests recommended by Theodore Tso. In that testing he ran into a WARN_ON_ONCE about a zero page refcount in try_get_page. The fix is in the latest version of patch 2. But it's already obsolete because John Hubbard is about to remove that function altogether.
I think the issues you raised were more uncertainty than known bugs. It seems the fact that you can have DAX pages with 0 refcount is a feature more than a bug.
Regards, Felix
Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? In that case, mmap() of a DAX device will call insert_page() which calls get_page() which would trigger VM_BUG_ON_PAGE().
I can believe it is OK for PTE_SPECIAL page table entries to have no struct page or that MEMORY_DEVICE_GENERIC struct pages be mapped with a zero reference count using insert_pfn().
Hi Ralph, We have tried the DAX tests with and without CONFIG_ARCH_HAS_PTE_SPECIAL defined. Apparently none of the tests touches that condition for a DAX device. Of course, that doesn't mean it could happen.
Regards, Alex S.
I find it hard to believe that other MM developers don't see an issue with a struct page with refcount == 0 and mapcount == 1.
I don't see where init_page_count() is being called for the MEMORY_DEVICE_GENERIC or MEMORY_DEVICE_PRIVATE struct pages the AMD driver allocates and passes to migrate_vma_setup(). Looks like svm_migrate_get_vram_page() needs to call init_page_count() instead of get_page(). (I'm looking at branch origin/alexsierrag/device_generic https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com...)
Yes, you're right. My bad. Thanks for catching this up. I didn't realize I was missing to define CONFIG_DEBUG_VM on my build. Therefore this BUG was never caught. It worked after I replaced get_pages by init_page_count at svm_migrate_get_vram_page. However, I don't think this is the best way to fix it.
You definitly don't want to do that. reiniting the page refcounter is wrong it should be done once. Nouveau is not a good example here.
Ideally, get_pages call should work for device pages with ref count equal to 0 too. Otherwise, we could overwrite refcounter if someone else is grabbing the page concurrently. I was thinking to add a special condition in get_pages for dev pages. This could also fix the insert_page -> get_page call from a DAX device.
What is the issue here exactly ?
Regards, Alex S.
Also, what about the other places where is_device_private_page() is called? Don't they need to be updated to call is_device_page() instead? One of my goals for this patch was to remove special casing reference counts for ZONE_DEVICE pages in rmap.c, etc.
Correct, is_device_private_page is still used in rmap, memcontrol and migrate.c files Looks like rmap and memcontrol should be replaced by is_device_page function.
No you do not want to do that. The private case is special case for a reason.
Jerome
The AMD architecture for the Frontier supercomputer will have device memory which can be coherently accessed by the CPU. The system BIOS advertises this memory as SPM (special purpose memory) in the UEFI system address map.
The AMDGPU driver needs to be able to lookup this resource in order to claim it as MEMORY_DEVICE_GENERIC using devm_memremap_pages.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- kernel/resource.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/resource.c b/kernel/resource.c index ca9f5198a01f..227fc9fab573 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -772,6 +772,7 @@ struct resource *lookup_resource(struct resource *root, resource_size_t start)
return res; } +EXPORT_SYMBOL_GPL(lookup_resource);
/* * Insert a resource into the resource tree. If successful, return NULL,
When CPU is connected throug XGMI, it has coherent access to VRAM resource. In this case that resource is taken from a table in the device gmc aperture base. This resource is used along with the device type, which could be DEVICE_PRIVATE or DEVICE_GENERIC to create the device page map region.
Signed-off-by: Alex Sierra alex.sierra@amd.com Reviewed-by: Felix Kuehling Felix.Kuehling@amd.com --- drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c index dab290a4d19d..24a8b6d4f947 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c @@ -868,6 +868,7 @@ int svm_migrate_init(struct amdgpu_device *adev) struct resource *res; unsigned long size; void *r; + bool xgmi_connected_to_cpu = adev->gmc.xgmi.connected_to_cpu;
/* Page migration works on Vega10 or newer */ if (kfddev->device_info->asic_family < CHIP_VEGA10) @@ -880,17 +881,22 @@ int svm_migrate_init(struct amdgpu_device *adev) * should remove reserved size */ size = ALIGN(adev->gmc.real_vram_size, 2ULL << 20); - res = devm_request_free_mem_region(adev->dev, &iomem_resource, size); + if (xgmi_connected_to_cpu) + res = lookup_resource(&iomem_resource, adev->gmc.aper_base); + else + res = devm_request_free_mem_region(adev->dev, &iomem_resource, size); + if (IS_ERR(res)) return -ENOMEM;
- pgmap->type = MEMORY_DEVICE_PRIVATE; pgmap->nr_range = 1; pgmap->range.start = res->start; pgmap->range.end = res->end; + pgmap->type = xgmi_connected_to_cpu ? + MEMORY_DEVICE_GENERIC : MEMORY_DEVICE_PRIVATE; pgmap->ops = &svm_migrate_pgmap_ops; pgmap->owner = SVM_ADEV_PGMAP_OWNER(adev); - pgmap->flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE; + pgmap->flags = 0; r = devm_memremap_pages(adev->dev, pgmap); if (IS_ERR(r)) { pr_err("failed to register HMM device memory\n"); @@ -914,6 +920,7 @@ void svm_migrate_fini(struct amdgpu_device *adev) struct dev_pagemap *pgmap = &adev->kfd.dev->pgmap;
devm_memunmap_pages(adev->dev, pgmap); - devm_release_mem_region(adev->dev, pgmap->range.start, - pgmap->range.end - pgmap->range.start + 1); + if (pgmap->type == MEMORY_DEVICE_PRIVATE) + devm_release_mem_region(adev->dev, pgmap->range.start, + pgmap->range.end - pgmap->range.start + 1); }
Generic device type memory on VRAM to RAM migration, has similar access as System RAM from the CPU. This flag sets the source from the sender. Which in Generic type case, should be set as SYSTEM.
Signed-off-by: Alex Sierra alex.sierra@amd.com Reviewed-by: Felix Kuehling Felix.Kuehling@amd.com --- drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c index 24a8b6d4f947..e5b10de83a5f 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c @@ -616,9 +616,12 @@ svm_migrate_vma_to_ram(struct amdgpu_device *adev, struct svm_range *prange, migrate.vma = vma; migrate.start = start; migrate.end = end; - migrate.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE; migrate.pgmap_owner = SVM_ADEV_PGMAP_OWNER(adev);
+ if (adev->gmc.xgmi.connected_to_cpu) + migrate.flags = MIGRATE_VMA_SELECT_SYSTEM; + else + migrate.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE; size = 2 * sizeof(*migrate.src) + sizeof(uint64_t) + sizeof(dma_addr_t); size *= npages; buf = kvmalloc(size, GFP_KERNEL | __GFP_ZERO);
Two helpers added. One checks if zone device page is generic type. The other if page is either private or generic type.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- include/linux/mm.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h index d48a1f0889d1..c25cdb92038f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1187,6 +1187,14 @@ static inline bool is_device_private_page(const struct page *page) page->pgmap->type == MEMORY_DEVICE_PRIVATE; }
+static inline bool is_device_page(const struct page *page) +{ + return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) && + is_zone_device_page(page) && + (page->pgmap->type == MEMORY_DEVICE_PRIVATE || + page->pgmap->type == MEMORY_DEVICE_GENERIC); +} + static inline bool is_pci_p2pdma_page(const struct page *page) { return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
Device generic type case added for migrate_vma_pages and migrate_vma_check_page helpers. Both, generic and private device types have the same conditions to decide to migrate pages from/to device memory.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- mm/migrate.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c index e3a10e2a1bb3..f9e6bfa2867c 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2565,7 +2565,7 @@ static bool migrate_vma_check_page(struct page *page) * FIXME proper solution is to rework migration_entry_wait() so * it does not need to take a reference on page. */ - return is_device_private_page(page); + return is_device_page(page); }
/* For file back page */ @@ -2854,7 +2854,7 @@ EXPORT_SYMBOL(migrate_vma_setup); * handle_pte_fault() * do_anonymous_page() * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE - * private page. + * private or generic page. */ static void migrate_vma_insert_page(struct migrate_vma *migrate, unsigned long addr, @@ -2925,10 +2925,14 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE); entry = swp_entry_to_pte(swp_entry); + } else if (is_device_page(page)) { + entry = mk_pte(page, vma->vm_page_prot); + if (vma->vm_flags & VM_WRITE) + entry = pte_mkwrite(pte_mkdirty(entry)); } else { /* - * For now we only support migrating to un-addressable - * device memory. + * We support migrating to private and generic types for device + * zone memory. */ pr_warn_once("Unsupported ZONE_DEVICE page type.\n"); goto abort; @@ -3034,10 +3038,10 @@ void migrate_vma_pages(struct migrate_vma *migrate) mapping = page_mapping(page);
if (is_zone_device_page(newpage)) { - if (is_device_private_page(newpage)) { + if (is_device_page(newpage)) { /* - * For now only support private anonymous when - * migrating to un-addressable device memory. + * For now only support private and generic + * anonymous when migrating to device memory. */ if (mapping) { migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
Add MEMORY_DEVICE_GENERIC case to free_zone_device_page callback. Device generic type memory case is now able to free its pages properly.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- mm/memremap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/memremap.c b/mm/memremap.c index 5aa8163fd948..5773e15b6ac9 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -459,7 +459,7 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, EXPORT_SYMBOL_GPL(get_dev_pagemap);
#ifdef CONFIG_DEV_PAGEMAP_OPS -static void free_device_private_page(struct page *page) +static void free_device_page(struct page *page) {
__ClearPageWaiters(page); @@ -498,7 +498,8 @@ void free_zone_device_page(struct page *page) wake_up_var(&page->_refcount); return; case MEMORY_DEVICE_PRIVATE: - free_device_private_page(page); + case MEMORY_DEVICE_GENERIC: + free_device_page(page); return; default: return;
new ioctl cmd added to query zone device type. This will be used once the test_hmm adds zone device generic type.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- lib/test_hmm.c | 15 ++++++++++++++- lib/test_hmm_uapi.h | 7 +++++++ 2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 6998f10350ea..3cd91ca31dd7 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -82,6 +82,7 @@ struct dmirror_chunk { struct dmirror_device { struct cdev cdevice; struct hmm_devmem *devmem; + unsigned int zone_device_type;
unsigned int devmem_capacity; unsigned int devmem_count; @@ -468,6 +469,7 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice, if (IS_ERR(res)) goto err_devmem;
+ mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PRIVATE; devmem->pagemap.type = MEMORY_DEVICE_PRIVATE; devmem->pagemap.range.start = res->start; devmem->pagemap.range.end = res->end; @@ -912,6 +914,15 @@ static int dmirror_snapshot(struct dmirror *dmirror, return ret; }
+static int dmirror_get_device_type(struct dmirror *dmirror, + struct hmm_dmirror_cmd *cmd) +{ + mutex_lock(&dmirror->mutex); + cmd->zone_device_type = dmirror->mdevice->zone_device_type; + mutex_unlock(&dmirror->mutex); + + return 0; +} static long dmirror_fops_unlocked_ioctl(struct file *filp, unsigned int command, unsigned long arg) @@ -952,7 +963,9 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp, case HMM_DMIRROR_SNAPSHOT: ret = dmirror_snapshot(dmirror, &cmd); break; - + case HMM_DMIRROR_GET_MEM_DEV_TYPE: + ret = dmirror_get_device_type(dmirror, &cmd); + break; default: return -EINVAL; } diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h index 670b4ef2a5b6..ee88701793d5 100644 --- a/lib/test_hmm_uapi.h +++ b/lib/test_hmm_uapi.h @@ -26,6 +26,7 @@ struct hmm_dmirror_cmd { __u64 npages; __u64 cpages; __u64 faults; + __u64 zone_device_type; };
/* Expose the address space of the calling process through hmm device file */ @@ -33,6 +34,7 @@ struct hmm_dmirror_cmd { #define HMM_DMIRROR_WRITE _IOWR('H', 0x01, struct hmm_dmirror_cmd) #define HMM_DMIRROR_MIGRATE _IOWR('H', 0x02, struct hmm_dmirror_cmd) #define HMM_DMIRROR_SNAPSHOT _IOWR('H', 0x03, struct hmm_dmirror_cmd) +#define HMM_DMIRROR_GET_MEM_DEV_TYPE _IOWR('H', 0x04, struct hmm_dmirror_cmd)
/* * Values returned in hmm_dmirror_cmd.ptr for HMM_DMIRROR_SNAPSHOT. @@ -60,4 +62,9 @@ enum { HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE = 0x30, };
+enum { + /* 0 is reserved to catch uninitialized type fields */ + HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1, +}; + #endif /* _LIB_TEST_HMM_UAPI_H */
In order to configure device generic in test_hmm, two module parameters should be passed, which correspon to the SP start address of each device (2) spm_addr_dev0 & spm_addr_dev1. If no parameters are passed, private device type is configured.
v5: Remove devmem->pagemap.type = MEMORY_DEVICE_PRIVATE at dmirror_allocate_chunk that was forcing to configure pagemap.type to MEMORY_DEVICE_PRIVATE
v6: Check for null pointers for resource and memremap references at dmirror_allocate_chunk
Signed-off-by: Alex Sierra alex.sierra@amd.com --- lib/test_hmm.c | 56 ++++++++++++++++++++++++++++++++------------- lib/test_hmm_uapi.h | 1 + 2 files changed, 41 insertions(+), 16 deletions(-)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 3cd91ca31dd7..b4f885c6c6ae 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -33,6 +33,16 @@ #define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U) #define DEVMEM_CHUNKS_RESERVE 16
+static unsigned long spm_addr_dev0; +module_param(spm_addr_dev0, long, 0644); +MODULE_PARM_DESC(spm_addr_dev0, + "Specify start address for SPM (special purpose memory) used for device 0. By setting this Generic device type will be used. Make sure spm_addr_dev1 is set too"); + +static unsigned long spm_addr_dev1; +module_param(spm_addr_dev1, long, 0644); +MODULE_PARM_DESC(spm_addr_dev1, + "Specify start address for SPM (special purpose memory) used for device 1. By setting this Generic device type will be used. Make sure spm_addr_dev0 is set too"); + static const struct dev_pagemap_ops dmirror_devmem_ops; static const struct mmu_interval_notifier_ops dmirror_min_ops; static dev_t dmirror_dev; @@ -450,11 +460,11 @@ static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd) return ret; }
-static bool dmirror_allocate_chunk(struct dmirror_device *mdevice, +static int dmirror_allocate_chunk(struct dmirror_device *mdevice, struct page **ppage) { struct dmirror_chunk *devmem; - struct resource *res; + struct resource *res = NULL; unsigned long pfn; unsigned long pfn_first; unsigned long pfn_last; @@ -462,15 +472,26 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
devmem = kzalloc(sizeof(*devmem), GFP_KERNEL); if (!devmem) - return false; + return -ENOMEM; + + if (!spm_addr_dev0 && !spm_addr_dev1) { + res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE, + "hmm_dmirror"); + devmem->pagemap.type = MEMORY_DEVICE_PRIVATE; + mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PRIVATE; + } else if (spm_addr_dev0 && spm_addr_dev1) { + res = lookup_resource(&iomem_resource, MINOR(mdevice->cdevice.dev) ? + spm_addr_dev0 : + spm_addr_dev1); + devmem->pagemap.type = MEMORY_DEVICE_GENERIC; + mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_GENERIC; + } else { + pr_err("Both spm_addr_dev parameters should be set\n"); + }
- res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE, - "hmm_dmirror"); - if (IS_ERR(res)) + if (IS_ERR_OR_NULL(res)) goto err_devmem;
- mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PRIVATE; - devmem->pagemap.type = MEMORY_DEVICE_PRIVATE; devmem->pagemap.range.start = res->start; devmem->pagemap.range.end = res->end; devmem->pagemap.nr_range = 1; @@ -493,10 +514,14 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice, mdevice->devmem_capacity = new_capacity; mdevice->devmem_chunks = new_chunks; } - ptr = memremap_pages(&devmem->pagemap, numa_node_id()); - if (IS_ERR(ptr)) + if (IS_ERR_OR_NULL(ptr)) { + if (ptr) + ret = PTR_ERR(ptr); + else + ret = -EFAULT; goto err_release; + }
devmem->mdevice = mdevice; pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT; @@ -1097,10 +1122,8 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id) if (ret) return ret;
- /* Build a list of free ZONE_DEVICE private struct pages */ - dmirror_allocate_chunk(mdevice, NULL); - - return 0; + /* Build a list of free ZONE_DEVICE struct pages */ + return dmirror_allocate_chunk(mdevice, NULL); }
static void dmirror_device_remove(struct dmirror_device *mdevice) @@ -1113,8 +1136,9 @@ static void dmirror_device_remove(struct dmirror_device *mdevice) mdevice->devmem_chunks[i];
memunmap_pages(&devmem->pagemap); - release_mem_region(devmem->pagemap.range.start, - range_len(&devmem->pagemap.range)); + if (devmem->pagemap.type == MEMORY_DEVICE_PRIVATE) + release_mem_region(devmem->pagemap.range.start, + range_len(&devmem->pagemap.range)); kfree(devmem); } kfree(mdevice->devmem_chunks); diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h index ee88701793d5..17a6b5059871 100644 --- a/lib/test_hmm_uapi.h +++ b/lib/test_hmm_uapi.h @@ -65,6 +65,7 @@ enum { enum { /* 0 is reserved to catch uninitialized type fields */ HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1, + HMM_DMIRROR_MEMORY_DEVICE_GENERIC, };
#endif /* _LIB_TEST_HMM_UAPI_H */
Device Generic type uses device memory that is coherently accesible by the CPU. Usually, this is shown as SP (special purpose) memory range at the BIOS-e820 memory enumeration. If no SP memory is supported in system, this could be faked by setting CONFIG_EFI_FAKE_MEMMAP.
Currently, test_hmm only supports two different SP ranges of at least 256MB size. This could be specified in the kernel parameter variable efi_fake_mem. Ex. Two SP ranges of 1GB starting at 0x100000000 & 0x140000000 physical address. efi_fake_mem=1G@0x100000000:0x40000,1G@0x140000000:0x40000
Signed-off-by: Alex Sierra alex.sierra@amd.com --- lib/test_hmm.c | 166 +++++++++++++++++++++++++++----------------- lib/test_hmm_uapi.h | 10 ++- 2 files changed, 113 insertions(+), 63 deletions(-)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c index b4f885c6c6ae..42edcc8eaad2 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -469,6 +469,7 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice, unsigned long pfn_first; unsigned long pfn_last; void *ptr; + int ret = -ENOMEM;
devmem = kzalloc(sizeof(*devmem), GFP_KERNEL); if (!devmem) @@ -550,7 +551,7 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice, } spin_unlock(&mdevice->lock);
- return true; + return 0;
err_release: mutex_unlock(&mdevice->devmem_lock); @@ -558,7 +559,7 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice, err_devmem: kfree(devmem);
- return false; + return ret; }
static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice) @@ -567,8 +568,10 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice) struct page *rpage;
/* - * This is a fake device so we alloc real system memory to store - * our device memory. + * For ZONE_DEVICE private type, this is a fake device so we alloc real + * system memory to store our device memory. + * For ZONE_DEVICE generic type we use the actual dpage to store the data + * and ignore rpage. */ rpage = alloc_page(GFP_HIGHUSER); if (!rpage) @@ -601,7 +604,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args, struct dmirror *dmirror) { struct dmirror_device *mdevice = dmirror->mdevice; - const unsigned long *src = args->src; + unsigned long *src = args->src; unsigned long *dst = args->dst; unsigned long addr;
@@ -619,12 +622,18 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args, * unallocated pte_none() or read-only zero page. */ spage = migrate_pfn_to_page(*src); - + if (spage && is_zone_device_page(spage)) { + pr_debug("page already in device spage pfn: 0x%lx\n", + page_to_pfn(spage)); + *src &= ~MIGRATE_PFN_MIGRATE; + continue; + } dpage = dmirror_devmem_alloc_page(mdevice); if (!dpage) continue;
- rpage = dpage->zone_device_data; + rpage = is_device_private_page(dpage) ? dpage->zone_device_data : + dpage; if (spage) copy_highpage(rpage, spage); else @@ -636,8 +645,10 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args, * the simulated device memory and that page holds the pointer * to the mirror. */ + rpage = dpage->zone_device_data; rpage->zone_device_data = dmirror; - + pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n", + page_to_pfn(spage), page_to_pfn(dpage)); *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED; if ((*src & MIGRATE_PFN_WRITE) || @@ -671,10 +682,13 @@ static int dmirror_migrate_finalize_and_map(struct migrate_vma *args, continue;
/* - * Store the page that holds the data so the page table - * doesn't have to deal with ZONE_DEVICE private pages. + * For ZONE_DEVICE private pages we store the page that + * holds the data so the page table doesn't have to deal it. + * For ZONE_DEVICE generic pages we store the actual page, since + * the CPU has coherent access to the page. */ - entry = dpage->zone_device_data; + entry = is_device_private_page(dpage) ? dpage->zone_device_data : + dpage; if (*dst & MIGRATE_PFN_WRITE) entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE); entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC); @@ -688,6 +702,47 @@ static int dmirror_migrate_finalize_and_map(struct migrate_vma *args, return 0; }
+static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args, + struct dmirror *dmirror) +{ + unsigned long *src = args->src; + unsigned long *dst = args->dst; + unsigned long start = args->start; + unsigned long end = args->end; + unsigned long addr; + + for (addr = start; addr < end; addr += PAGE_SIZE, + src++, dst++) { + struct page *dpage, *spage; + + spage = migrate_pfn_to_page(*src); + if (!spage || !(*src & MIGRATE_PFN_MIGRATE)) + continue; + if (is_device_private_page(spage)) { + spage = spage->zone_device_data; + } else { + pr_debug("page already in system or SPM spage pfn: 0x%lx\n", + page_to_pfn(spage)); + *src &= ~MIGRATE_PFN_MIGRATE; + continue; + } + dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr); + if (!dpage) + continue; + pr_debug("migrating from dev to sys pfn src: 0x%lx pfn dst: 0x%lx\n", + page_to_pfn(spage), page_to_pfn(dpage)); + + lock_page(dpage); + xa_erase(&dmirror->pt, addr >> PAGE_SHIFT); + copy_highpage(dpage, spage); + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED; + if (*src & MIGRATE_PFN_WRITE) + *dst |= MIGRATE_PFN_WRITE; + } + return 0; +} + + static int dmirror_migrate(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd) { @@ -729,33 +784,46 @@ static int dmirror_migrate(struct dmirror *dmirror, args.start = addr; args.end = next; args.pgmap_owner = dmirror->mdevice; - args.flags = MIGRATE_VMA_SELECT_SYSTEM; + args.flags = (!cmd->alloc_to_devmem && + dmirror->mdevice->zone_device_type == + HMM_DMIRROR_MEMORY_DEVICE_PRIVATE) ? + MIGRATE_VMA_SELECT_DEVICE_PRIVATE : + MIGRATE_VMA_SELECT_SYSTEM; ret = migrate_vma_setup(&args); if (ret) goto out;
- dmirror_migrate_alloc_and_copy(&args, dmirror); + if (cmd->alloc_to_devmem) { + pr_debug("Migrating from sys mem to device mem\n"); + dmirror_migrate_alloc_and_copy(&args, dmirror); + } else { + pr_debug("Migrating from device mem to sys mem\n"); + dmirror_devmem_fault_alloc_and_copy(&args, dmirror); + } migrate_vma_pages(&args); - dmirror_migrate_finalize_and_map(&args, dmirror); + if (cmd->alloc_to_devmem) + dmirror_migrate_finalize_and_map(&args, dmirror); migrate_vma_finalize(&args); } mmap_read_unlock(mm); mmput(mm);
- /* Return the migrated data for verification. */ - ret = dmirror_bounce_init(&bounce, start, size); - if (ret) - return ret; - mutex_lock(&dmirror->mutex); - ret = dmirror_do_read(dmirror, start, end, &bounce); - mutex_unlock(&dmirror->mutex); - if (ret == 0) { - if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr, - bounce.size)) - ret = -EFAULT; + /* Return the migrated data for verification. only for pages in device zone */ + if (cmd->alloc_to_devmem) { + ret = dmirror_bounce_init(&bounce, start, size); + if (ret) + return ret; + mutex_lock(&dmirror->mutex); + ret = dmirror_do_read(dmirror, start, end, &bounce); + mutex_unlock(&dmirror->mutex); + if (ret == 0) { + if (copy_to_user(u64_to_user_ptr(cmd->ptr), bounce.ptr, + bounce.size)) + ret = -EFAULT; + } + cmd->cpages = bounce.cpages; + dmirror_bounce_fini(&bounce); } - cmd->cpages = bounce.cpages; - dmirror_bounce_fini(&bounce); return ret;
out: @@ -779,9 +847,15 @@ static void dmirror_mkentry(struct dmirror *dmirror, struct hmm_range *range, }
page = hmm_pfn_to_page(entry); - if (is_device_private_page(page)) { - /* Is the page migrated to this device or some other? */ - if (dmirror->mdevice == dmirror_page_to_device(page)) + if (is_device_page(page)) { + /* Is page ZONE_DEVICE generic? */ + if (!is_device_private_page(page)) + *perm = HMM_DMIRROR_PROT_DEV_GENERIC; + /* + * Is page ZONE_DEVICE private migrated to + * this device or some other? + */ + else if (dmirror->mdevice == dmirror_page_to_device(page)) *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL; else *perm = HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE; @@ -1028,38 +1102,6 @@ static void dmirror_devmem_free(struct page *page) spin_unlock(&mdevice->lock); }
-static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args, - struct dmirror *dmirror) -{ - const unsigned long *src = args->src; - unsigned long *dst = args->dst; - unsigned long start = args->start; - unsigned long end = args->end; - unsigned long addr; - - for (addr = start; addr < end; addr += PAGE_SIZE, - src++, dst++) { - struct page *dpage, *spage; - - spage = migrate_pfn_to_page(*src); - if (!spage || !(*src & MIGRATE_PFN_MIGRATE)) - continue; - spage = spage->zone_device_data; - - dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr); - if (!dpage) - continue; - - lock_page(dpage); - xa_erase(&dmirror->pt, addr >> PAGE_SHIFT); - copy_highpage(dpage, spage); - *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED; - if (*src & MIGRATE_PFN_WRITE) - *dst |= MIGRATE_PFN_WRITE; - } - return 0; -} - static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf) { struct migrate_vma args; diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h index 17a6b5059871..1f2322286fba 100644 --- a/lib/test_hmm_uapi.h +++ b/lib/test_hmm_uapi.h @@ -17,8 +17,12 @@ * @addr: (in) user address the device will read/write * @ptr: (in) user address where device data is copied to/from * @npages: (in) number of pages to read/write + * @alloc_to_devmem: (in) desired allocation destination during migration. + * True if allocation is to device memory. + * False if allocation is to system memory. * @cpages: (out) number of pages copied * @faults: (out) number of device page faults seen + * @zone_device_type: (out) zone device memory type */ struct hmm_dmirror_cmd { __u64 addr; @@ -26,7 +30,8 @@ struct hmm_dmirror_cmd { __u64 npages; __u64 cpages; __u64 faults; - __u64 zone_device_type; + __u32 zone_device_type; + __u32 alloc_to_devmem; };
/* Expose the address space of the calling process through hmm device file */ @@ -49,6 +54,8 @@ struct hmm_dmirror_cmd { * device the ioctl() is made * HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE: Migrated device private page on some * other device + * HMM_DMIRROR_PROT_DEV_GENERIC: Migrate device generic page on the device + * the ioctl() is made */ enum { HMM_DMIRROR_PROT_ERROR = 0xFF, @@ -60,6 +67,7 @@ enum { HMM_DMIRROR_PROT_ZERO = 0x10, HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL = 0x20, HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE = 0x30, + HMM_DMIRROR_PROT_DEV_GENERIC = 0x40, };
enum {
Test cases such as migrate_fault and migrate_multiple, were modified to explicit migrate from device to sys memory without the need of page faults, when using device generic type.
Snapshot test case updated to read memory device type first and based on that, get the proper returned results migrate_ping_pong test case added to test explicit migration from device to sys memory for both private and generic zone types.
Helpers to migrate from device to sys memory and vicerversa were also added.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- tools/testing/selftests/vm/hmm-tests.c | 142 +++++++++++++++++++++---- 1 file changed, 124 insertions(+), 18 deletions(-)
diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c index 5d1ac691b9f4..70632b195497 100644 --- a/tools/testing/selftests/vm/hmm-tests.c +++ b/tools/testing/selftests/vm/hmm-tests.c @@ -44,6 +44,8 @@ struct hmm_buffer { int fd; uint64_t cpages; uint64_t faults; + int zone_device_type; + bool alloc_to_devmem; };
#define TWOMEG (1 << 21) @@ -133,6 +135,7 @@ static int hmm_dmirror_cmd(int fd, cmd.addr = (__u64)buffer->ptr; cmd.ptr = (__u64)buffer->mirror; cmd.npages = npages; + cmd.alloc_to_devmem = buffer->alloc_to_devmem;
for (;;) { ret = ioctl(fd, request, &cmd); @@ -144,6 +147,7 @@ static int hmm_dmirror_cmd(int fd, } buffer->cpages = cmd.cpages; buffer->faults = cmd.faults; + buffer->zone_device_type = cmd.zone_device_type;
return 0; } @@ -211,6 +215,34 @@ static void hmm_nanosleep(unsigned int n) nanosleep(&t, NULL); }
+static int hmm_migrate_sys_to_dev(int fd, + struct hmm_buffer *buffer, + unsigned long npages) +{ + buffer->alloc_to_devmem = true; + return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE, buffer, npages); +} + +static int hmm_migrate_dev_to_sys(int fd, + struct hmm_buffer *buffer, + unsigned long npages) +{ + buffer->alloc_to_devmem = false; + return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE, buffer, npages); +} + +static int hmm_is_private_device(int fd, bool *res) +{ + struct hmm_buffer buffer; + int ret; + + buffer.ptr = 0; + ret = hmm_dmirror_cmd(fd, HMM_DMIRROR_GET_MEM_DEV_TYPE, &buffer, 1); + *res = (buffer.zone_device_type == HMM_DMIRROR_MEMORY_DEVICE_PRIVATE); + + return ret; +} + /* * Simple NULL test of device open/close. */ @@ -875,7 +907,7 @@ TEST_F(hmm, migrate) ptr[i] = i;
/* Migrate memory to device. */ - ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages); + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages);
@@ -923,7 +955,7 @@ TEST_F(hmm, migrate_fault) ptr[i] = i;
/* Migrate memory to device. */ - ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages); + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages);
@@ -936,7 +968,7 @@ TEST_F(hmm, migrate_fault) ASSERT_EQ(ptr[i], i);
/* Migrate memory to the device again. */ - ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages); + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages);
@@ -976,7 +1008,7 @@ TEST_F(hmm, migrate_shared) ASSERT_NE(buffer->ptr, MAP_FAILED);
/* Migrate memory to device. */ - ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages); + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); ASSERT_EQ(ret, -ENOENT);
hmm_buffer_free(buffer); @@ -1015,7 +1047,7 @@ TEST_F(hmm2, migrate_mixed) p = buffer->ptr;
/* Migrating a protected area should be an error. */ - ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, npages); + ret = hmm_migrate_sys_to_dev(self->fd1, buffer, npages); ASSERT_EQ(ret, -EINVAL);
/* Punch a hole after the first page address. */ @@ -1023,7 +1055,7 @@ TEST_F(hmm2, migrate_mixed) ASSERT_EQ(ret, 0);
/* We expect an error if the vma doesn't cover the range. */ - ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 3); + ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 3); ASSERT_EQ(ret, -EINVAL);
/* Page 2 will be a read-only zero page. */ @@ -1055,13 +1087,13 @@ TEST_F(hmm2, migrate_mixed)
/* Now try to migrate pages 2-5 to device 1. */ buffer->ptr = p + 2 * self->page_size; - ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 4); + ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 4); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, 4);
/* Page 5 won't be migrated to device 0 because it's on device 1. */ buffer->ptr = p + 5 * self->page_size; - ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1); + ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1); ASSERT_EQ(ret, -ENOENT); buffer->ptr = p;
@@ -1070,8 +1102,12 @@ TEST_F(hmm2, migrate_mixed) }
/* - * Migrate anonymous memory to device private memory and fault it back to system - * memory multiple times. + * Migrate anonymous memory to device memory and back to system memory + * multiple times. In case of private zone configuration, this is done + * through fault pages accessed by CPU. In case of generic zone configuration, + * the pages from the device should be explicitly migrated back to system memory. + * The reason is Generic device zone has coherent access to CPU, therefore + * it will not generate any page fault. */ TEST_F(hmm, migrate_multiple) { @@ -1082,7 +1118,9 @@ TEST_F(hmm, migrate_multiple) unsigned long c; int *ptr; int ret; + bool is_private;
+ ASSERT_EQ(hmm_is_private_device(self->fd, &is_private), 0); npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; ASSERT_NE(npages, 0); size = npages << self->page_shift; @@ -1107,8 +1145,7 @@ TEST_F(hmm, migrate_multiple) ptr[i] = i;
/* Migrate memory to device. */ - ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, - npages); + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages);
@@ -1116,7 +1153,12 @@ TEST_F(hmm, migrate_multiple) for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i) ASSERT_EQ(ptr[i], i);
- /* Fault pages back to system memory and check them. */ + /* Migrate back to system memory and check them. */ + if (!is_private) { + ret = hmm_migrate_dev_to_sys(self->fd, buffer, npages); + ASSERT_EQ(ret, 0); + } + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) ASSERT_EQ(ptr[i], i);
@@ -1261,10 +1303,12 @@ TEST_F(hmm2, snapshot) unsigned char *m; int ret; int val; + bool is_private;
npages = 7; size = npages << self->page_shift;
+ ASSERT_EQ(hmm_is_private_device(self->fd0, &is_private), 0); buffer = malloc(sizeof(*buffer)); ASSERT_NE(buffer, NULL);
@@ -1312,13 +1356,13 @@ TEST_F(hmm2, snapshot)
/* Page 5 will be migrated to device 0. */ buffer->ptr = p + 5 * self->page_size; - ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1); + ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, 1);
/* Page 6 will be migrated to device 1. */ buffer->ptr = p + 6 * self->page_size; - ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 1); + ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 1); ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, 1);
@@ -1335,9 +1379,16 @@ TEST_F(hmm2, snapshot) ASSERT_EQ(m[2], HMM_DMIRROR_PROT_ZERO | HMM_DMIRROR_PROT_READ); ASSERT_EQ(m[3], HMM_DMIRROR_PROT_READ); ASSERT_EQ(m[4], HMM_DMIRROR_PROT_WRITE); - ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL | - HMM_DMIRROR_PROT_WRITE); - ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE); + if (is_private) { + ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL | + HMM_DMIRROR_PROT_WRITE); + ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE); + } else { + ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_GENERIC | + HMM_DMIRROR_PROT_WRITE); + ASSERT_EQ(m[6], HMM_DMIRROR_PROT_DEV_GENERIC | + HMM_DMIRROR_PROT_WRITE); + }
hmm_buffer_free(buffer); } @@ -1485,4 +1536,59 @@ TEST_F(hmm2, double_map) hmm_buffer_free(buffer); }
+/* + * Migrate anonymous memory to device memory and migrate back to system memory + * explicitly, without generating a page fault. + */ +TEST_F(hmm, migrate_ping_pong) +{ + struct hmm_buffer *buffer; + unsigned long npages; + unsigned long size; + unsigned long i; + int *ptr; + int ret; + + npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; + ASSERT_NE(npages, 0); + size = npages << self->page_shift; + + buffer = malloc(sizeof(*buffer)); + ASSERT_NE(buffer, NULL); + + buffer->fd = -1; + buffer->size = size; + buffer->mirror = malloc(size); + buffer->alloc_to_devmem = true; + ASSERT_NE(buffer->mirror, NULL); + + buffer->ptr = mmap(NULL, size, + PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, + buffer->fd, 0); + ASSERT_NE(buffer->ptr, MAP_FAILED); + + /* Initialize buffer in system memory. */ + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ptr[i] = i; + + /* Migrate memory to device. */ + ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); + ASSERT_EQ(ret, 0); + ASSERT_EQ(buffer->cpages, npages); + /* Check what the device read. */ + for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i], i); + + /* Migrate memory back to system mem. */ + ret = hmm_migrate_dev_to_sys(self->fd, buffer, npages); + ASSERT_EQ(ret, 0); + + /* Check the buffer migrated back to system memory. */ + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i], i); + + hmm_buffer_free(buffer); +} + TEST_HARNESS_MAIN
Add two more parameters to set spm_addr_dev0 & spm_addr_dev1 addresses. These two parameters configure the start SP addresses for each device in test_hmm driver. Consequently, this configures zone device type as generic.
Signed-off-by: Alex Sierra alex.sierra@amd.com --- tools/testing/selftests/vm/test_hmm.sh | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/vm/test_hmm.sh b/tools/testing/selftests/vm/test_hmm.sh index 0647b525a625..3eeabe94399f 100755 --- a/tools/testing/selftests/vm/test_hmm.sh +++ b/tools/testing/selftests/vm/test_hmm.sh @@ -40,7 +40,18 @@ check_test_requirements()
load_driver() { - modprobe $DRIVER > /dev/null 2>&1 + if [ $# -eq 0 ]; then + modprobe $DRIVER > /dev/null 2>&1 + else + if [ $# -eq 2 ]; then + modprobe $DRIVER spm_addr_dev0=$1 spm_addr_dev1=$2 + > /dev/null 2>&1 + else + echo "Missing module parameters. Make sure pass"\ + "spm_addr_dev0 and spm_addr_dev1" + usage + fi + fi if [ $? == 0 ]; then major=$(awk "$2=="HMM_DMIRROR" {print $1}" /proc/devices) mknod /dev/hmm_dmirror0 c $major 0 @@ -58,7 +69,7 @@ run_smoke() { echo "Running smoke test. Note, this test provides basic coverage."
- load_driver + load_driver $1 $2 $(dirname "${BASH_SOURCE[0]}")/hmm-tests unload_driver } @@ -75,6 +86,9 @@ usage() echo "# Smoke testing" echo "./${TEST_NAME}.sh smoke" echo + echo "# Smoke testing with SPM enabled" + echo "./${TEST_NAME}.sh smoke <spm_addr_dev0> <spm_addr_dev1>" + echo exit 0 }
@@ -84,7 +98,7 @@ function run_test() usage else if [ "$1" = "smoke" ]; then - run_smoke + run_smoke $2 $3 else usage fi
dri-devel@lists.freedesktop.org
-
Alex Sierra -
Felix Kuehling -
Jerome Glisse -
Ralph Campbell -
Sierra Guiza, Alejandro (Alex)