From: Jason Gunthorpe jgg@mellanox.com
hmm_vma_walk->last is supposed to be updated after every write to the pfns, so that it can be returned by hmm_range_fault(). However, this is not done consistently. Fortunately nothing checks the return code of hmm_range_fault() for anything other than error.
More importantly last must be set before returning -EBUSY as it is used to prevent reading an output pfn as an input flags when the loop restarts.
For clarity and simplicity make hmm_range_fault() return 0 or -ERRNO. Only set last when returning -EBUSY.
Acked-by: Felix Kuehling Felix.Kuehling@amd.com Tested-by: Ralph Campbell rcampbell@nvidia.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Jason Gunthorpe jgg@mellanox.com --- Documentation/vm/hmm.rst | 2 +- drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 ++-- drivers/gpu/drm/nouveau/nouveau_svm.c | 6 +++--- include/linux/hmm.h | 2 +- mm/hmm.c | 25 +++++++++---------------- 5 files changed, 16 insertions(+), 23 deletions(-)
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 4e3e9362afeb10..9924f2caa0184c 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -161,7 +161,7 @@ device must complete the update before the driver callback returns. When the device driver wants to populate a range of virtual addresses, it can use::
- long hmm_range_fault(struct hmm_range *range); + int hmm_range_fault(struct hmm_range *range);
It will trigger a page fault on missing or read-only entries if write access is requested (see below). Page faults use the generic mm page fault code path just diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index 6309ff72bd7876..7eb745b8acce0f 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -852,12 +852,12 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages) down_read(&mm->mmap_sem); r = hmm_range_fault(range); up_read(&mm->mmap_sem); - if (unlikely(r <= 0)) { + if (unlikely(r)) { /* * FIXME: This timeout should encompass the retry from * mmu_interval_read_retry() as well. */ - if ((r == 0 || r == -EBUSY) && !time_after(jiffies, timeout)) + if (r == -EBUSY && !time_after(jiffies, timeout)) goto retry; goto out_free_pfns; } diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c index 645fedd77e21b4..c68e9317cf0740 100644 --- a/drivers/gpu/drm/nouveau/nouveau_svm.c +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c @@ -536,7 +536,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm, .pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT, }; struct mm_struct *mm = notifier->notifier.mm; - long ret; + int ret;
while (true) { if (time_after(jiffies, timeout)) @@ -548,8 +548,8 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm, down_read(&mm->mmap_sem); ret = hmm_range_fault(&range); up_read(&mm->mmap_sem); - if (ret <= 0) { - if (ret == 0 || ret == -EBUSY) + if (ret) { + if (ret == -EBUSY) continue; return ret; } diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 7475051100c782..0df27dd03d53d7 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -120,7 +120,7 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang /* * Please see Documentation/vm/hmm.rst for how to use the range API. */ -long hmm_range_fault(struct hmm_range *range); +int hmm_range_fault(struct hmm_range *range);
/* * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range diff --git a/mm/hmm.c b/mm/hmm.c index 280585833adfc1..f06bcac948a79b 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -174,7 +174,6 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end, } if (required_fault) return hmm_vma_fault(addr, end, required_fault, walk); - hmm_vma_walk->last = addr; return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE); }
@@ -207,7 +206,6 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; - hmm_vma_walk->last = end; return 0; } #else /* CONFIG_TRANSPARENT_HUGEPAGE */ @@ -386,13 +384,10 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, pfns); if (r) { /* hmm_vma_handle_pte() did pte_unmap() */ - hmm_vma_walk->last = addr; return r; } } pte_unmap(ptep - 1); - - hmm_vma_walk->last = addr; return 0; }
@@ -455,7 +450,6 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, for (i = 0; i < npages; ++i, ++pfn) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; - hmm_vma_walk->last = end; goto out_unlock; }
@@ -500,7 +494,6 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask, for (; addr < end; addr += PAGE_SIZE, i++, pfn++) range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; - hmm_vma_walk->last = end; spin_unlock(ptl); return 0; } @@ -537,7 +530,6 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end, return -EFAULT;
hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); - hmm_vma_walk->last = end;
/* Skip this vma and continue processing the next vma. */ return 1; @@ -555,9 +547,7 @@ static const struct mm_walk_ops hmm_walk_ops = { * hmm_range_fault - try to fault some address in a virtual address range * @range: argument structure * - * Return: the number of valid pages in range->pfns[] (from range start - * address), which may be zero. On error one of the following status codes - * can be returned: + * Returns 0 on success or one of the following error codes: * * -EINVAL: Invalid arguments or mm or virtual address is in an invalid vma * (e.g., device file vma). @@ -572,7 +562,7 @@ static const struct mm_walk_ops hmm_walk_ops = { * This is similar to get_user_pages(), except that it can read the page tables * without mutating them (ie causing faults). */ -long hmm_range_fault(struct hmm_range *range) +int hmm_range_fault(struct hmm_range *range) { struct hmm_vma_walk hmm_vma_walk = { .range = range, @@ -590,10 +580,13 @@ long hmm_range_fault(struct hmm_range *range) return -EBUSY; ret = walk_page_range(mm, hmm_vma_walk.last, range->end, &hmm_walk_ops, &hmm_vma_walk); + /* + * When -EBUSY is returned the loop restarts with + * hmm_vma_walk.last set to an address that has not been stored + * in pfns. All entries < last in the pfn array are set to their + * output, and all >= are still at their input values. + */ } while (ret == -EBUSY); - - if (ret) - return ret; - return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT; + return ret; } EXPORT_SYMBOL(hmm_range_fault);