hmm_range_fault related fixes and legacy API removal v3

hmm_range_fault related fixes and legacy API removal v3

[Christoph Hellwig]

Hi Jérôme, Ben, Felxi and Jason,

below is a series against the hmm tree which cleans up various minor
bits and allows HMM_MIRROR to be built on all architectures.

Diffstat:

    7 files changed, 81 insertions(+), 171 deletions(-)

A git tree is also available at:

    git://git.infradead.org/users/hch/misc.git hmm-cleanups

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/hmm-cleanups

[PATCH 01/13] amdgpu: remove -EAGAIN handling for hmm_range_fault

[Christoph Hellwig]

hmm_range_fault can only return -EAGAIN if called with the block
argument set to false, so remove the special handling for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 23 +++--------------------
 1 file changed, 3 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 12a59ac83f72..f0821638bbc6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -778,7 +778,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 	struct hmm_range *range;
 	unsigned long i;
 	uint64_t *pfns;
-	int retry = 0;
 	int r = 0;
 
 	if (!mm) /* Happens during process shutdown */
@@ -822,7 +821,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 	hmm_range_register(range, mirror, start,
 			   start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);
 
-retry:
 	/*
 	 * Just wait for range to be valid, safe to ignore return value as we
 	 * will use the return value of hmm_range_fault() below under the
@@ -831,24 +829,12 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 	hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT);
 
 	down_read(&mm->mmap_sem);
-
 	r = hmm_range_fault(range, 0);
-	if (unlikely(r < 0)) {
-		if (likely(r == -EAGAIN)) {
-			/*
-			 * return -EAGAIN, mmap_sem is dropped
-			 */
-			if (retry++ < MAX_RETRY_HMM_RANGE_FAULT)
-				goto retry;
-			else
-				pr_err("Retry hmm fault too many times\n");
-		}
-
-		goto out_up_read;
-	}
-
 	up_read(&mm->mmap_sem);
 
+	if (unlikely(r < 0))
+		goto out_free_pfns;
+
 	for (i = 0; i < ttm->num_pages; i++) {
 		pages[i] = hmm_device_entry_to_page(range, pfns[i]);
 		if (unlikely(!pages[i])) {
@@ -864,9 +850,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 
 	return 0;
 
-out_up_read:
-	if (likely(r != -EAGAIN))
-		up_read(&mm->mmap_sem);
 out_free_pfns:
 	hmm_range_unregister(range);
 	kvfree(pfns);
-- 
2.20.1

[PATCH 02/13] amdgpu: don't initialize range->list in amdgpu_hmm_init_range

[Christoph Hellwig]

The list is used to add the range to another list as an entry in the
core hmm code, so there is no need to initialize it in a driver.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
index b698b423b25d..60b9fc9561d7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
@@ -484,6 +484,5 @@ void amdgpu_hmm_init_range(struct hmm_range *range)
 		range->flags = hmm_range_flags;
 		range->values = hmm_range_values;
 		range->pfn_shift = PAGE_SHIFT;
-		INIT_LIST_HEAD(&range->list);
 	}
 }
-- 
2.20.1

[PATCH 03/13] nouveau: pass struct nouveau_svmm to nouveau_range_fault

[Christoph Hellwig]

This avoid having to abuse the vma field in struct hmm_range to unlock
the mmap_sem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/gpu/drm/nouveau/nouveau_svm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index a74530b5a523..b889d5ec4c7e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -485,14 +485,14 @@ nouveau_range_done(struct hmm_range *range)
 }
 
 static int
-nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range)
+nouveau_range_fault(struct nouveau_svmm *svmm, struct hmm_range *range)
 {
 	long ret;
 
 	range->default_flags = 0;
 	range->pfn_flags_mask = -1UL;
 
-	ret = hmm_range_register(range, mirror,
+	ret = hmm_range_register(range, &svmm->mirror,
 				 range->start, range->end,
 				 PAGE_SHIFT);
 	if (ret) {
@@ -689,7 +689,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
 		range.values = nouveau_svm_pfn_values;
 		range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT;
 again:
-		ret = nouveau_range_fault(&svmm->mirror, &range);
+		ret = nouveau_range_fault(svmm, &range);
 		if (ret == 0) {
 			mutex_lock(&svmm->mutex);
 			if (!nouveau_range_done(&range)) {
-- 
2.20.1

[PATCH 04/13] mm: remove the pgmap field from struct hmm_vma_walk

[Christoph Hellwig]

There is only a single place where the pgmap is passed over a function
call, so replace it with local variables in the places where we deal
with the pgmap.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 62 ++++++++++++++++++++++++--------------------------------
 1 file changed, 27 insertions(+), 35 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 9a908902e4cc..d66fa29b42e0 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -278,7 +278,6 @@ EXPORT_SYMBOL(hmm_mirror_unregister);
 
 struct hmm_vma_walk {
 	struct hmm_range	*range;
-	struct dev_pagemap	*pgmap;
 	unsigned long		last;
 	unsigned int		flags;
 };
@@ -475,6 +474,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
+	struct dev_pagemap *pgmap = NULL;
 	unsigned long pfn, npages, i;
 	bool fault, write_fault;
 	uint64_t cpu_flags;
@@ -490,17 +490,14 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 	pfn = pmd_pfn(pmd) + pte_index(addr);
 	for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
 		if (pmd_devmap(pmd)) {
-			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
-					      hmm_vma_walk->pgmap);
-			if (unlikely(!hmm_vma_walk->pgmap))
+			pgmap = get_dev_pagemap(pfn, pgmap);
+			if (unlikely(!pgmap))
 				return -EBUSY;
 		}
 		pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
 	}
-	if (hmm_vma_walk->pgmap) {
-		put_dev_pagemap(hmm_vma_walk->pgmap);
-		hmm_vma_walk->pgmap = NULL;
-	}
+	if (pgmap)
+		put_dev_pagemap(pgmap);
 	hmm_vma_walk->last = end;
 	return 0;
 #else
@@ -520,7 +517,7 @@ static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 
 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 			      unsigned long end, pmd_t *pmdp, pte_t *ptep,
-			      uint64_t *pfn)
+			      uint64_t *pfn, struct dev_pagemap **pgmap)
 {
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
@@ -591,9 +588,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 		goto fault;
 
 	if (pte_devmap(pte)) {
-		hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte),
-					      hmm_vma_walk->pgmap);
-		if (unlikely(!hmm_vma_walk->pgmap))
+		*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
+		if (unlikely(!*pgmap))
 			return -EBUSY;
 	} else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
 		*pfn = range->values[HMM_PFN_SPECIAL];
@@ -604,10 +600,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 	return 0;
 
 fault:
-	if (hmm_vma_walk->pgmap) {
-		put_dev_pagemap(hmm_vma_walk->pgmap);
-		hmm_vma_walk->pgmap = NULL;
-	}
+	if (*pgmap)
+		put_dev_pagemap(*pgmap);
+	*pgmap = NULL;
+
 	pte_unmap(ptep);
 	/* Fault any virtual address we were asked to fault */
 	return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
@@ -620,6 +616,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 {
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
+	struct dev_pagemap *pgmap = NULL;
 	uint64_t *pfns = range->pfns;
 	unsigned long addr = start, i;
 	pte_t *ptep;
@@ -683,23 +680,21 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 	for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
 		int r;
 
-		r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
+		r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i],
+				&pgmap);
 		if (r) {
 			/* hmm_vma_handle_pte() did unmap pte directory */
 			hmm_vma_walk->last = addr;
 			return r;
 		}
 	}
-	if (hmm_vma_walk->pgmap) {
-		/*
-		 * We do put_dev_pagemap() here and not in hmm_vma_handle_pte()
-		 * so that we can leverage get_dev_pagemap() optimization which
-		 * will not re-take a reference on a pgmap if we already have
-		 * one.
-		 */
-		put_dev_pagemap(hmm_vma_walk->pgmap);
-		hmm_vma_walk->pgmap = NULL;
-	}
+	/*
+	 * We do put_dev_pagemap() here and not in hmm_vma_handle_pte() so that
+	 * we can leverage the get_dev_pagemap() optimization which will not
+	 * re-take a reference on a pgmap if we already have one.
+	 */
+	if (pgmap)
+		put_dev_pagemap(pgmap);
 	pte_unmap(ptep - 1);
 
 	hmm_vma_walk->last = addr;
@@ -714,6 +709,7 @@ static int hmm_vma_walk_pud(pud_t *pudp,
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	unsigned long addr = start, next;
+	struct dev_pagemap *pgmap = NULL;
 	pmd_t *pmdp;
 	pud_t pud;
 	int ret;
@@ -744,17 +740,14 @@ static int hmm_vma_walk_pud(pud_t *pudp,
 
 		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 		for (i = 0; i < npages; ++i, ++pfn) {
-			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
-					      hmm_vma_walk->pgmap);
-			if (unlikely(!hmm_vma_walk->pgmap))
+			pgmap = get_dev_pagemap(pfn, pgmap);
+			if (unlikely(!pgmap))
 				return -EBUSY;
 			pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 				  cpu_flags;
 		}
-		if (hmm_vma_walk->pgmap) {
-			put_dev_pagemap(hmm_vma_walk->pgmap);
-			hmm_vma_walk->pgmap = NULL;
-		}
+		if (pgmap)
+			put_dev_pagemap(pgmap);
 		hmm_vma_walk->last = end;
 		return 0;
 	}
@@ -1002,7 +995,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 			return -EPERM;
 		}
 
-		hmm_vma_walk.pgmap = NULL;
 		hmm_vma_walk.last = start;
 		hmm_vma_walk.flags = flags;
 		hmm_vma_walk.range = range;
-- 
2.20.1

[PATCH 05/13] mm: remove the unused vma argument to hmm_range_dma_unmap

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/hmm.h | 1 -
 mm/hmm.c            | 2 --
 2 files changed, 3 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 82265118d94a..59be0aa2476d 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -422,7 +422,6 @@ long hmm_range_dma_map(struct hmm_range *range,
 		       dma_addr_t *daddrs,
 		       unsigned int flags);
 long hmm_range_dma_unmap(struct hmm_range *range,
-			 struct vm_area_struct *vma,
 			 struct device *device,
 			 dma_addr_t *daddrs,
 			 bool dirty);
diff --git a/mm/hmm.c b/mm/hmm.c
index d66fa29b42e0..3a3852660757 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1121,7 +1121,6 @@ EXPORT_SYMBOL(hmm_range_dma_map);
 /**
  * hmm_range_dma_unmap() - unmap range of that was map with hmm_range_dma_map()
  * @range: range being unmapped
- * @vma: the vma against which the range (optional)
  * @device: device against which dma map was done
  * @daddrs: dma address of mapped pages
  * @dirty: dirty page if it had the write flag set
@@ -1133,7 +1132,6 @@ EXPORT_SYMBOL(hmm_range_dma_map);
  * concurrent mmu notifier or sync_cpu_device_pagetables() to make progress.
  */
 long hmm_range_dma_unmap(struct hmm_range *range,
-			 struct vm_area_struct *vma,
 			 struct device *device,
 			 dma_addr_t *daddrs,
 			 bool dirty)
-- 
2.20.1

[PATCH 06/13] mm: remove superflous arguments from hmm_range_register

[Christoph Hellwig]

The start, end and page_shift values are all saved in the range
structure, so we might as well use that for argument passing.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/vm/hmm.rst                |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  7 +++++--
 drivers/gpu/drm/nouveau/nouveau_svm.c   |  5 ++---
 include/linux/hmm.h                     |  6 +-----
 mm/hmm.c                                | 20 +++++---------------
 5 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index ddcb5ca8b296..e63c11f7e0e0 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -222,7 +222,7 @@ The usage pattern is::
       range.flags = ...;
       range.values = ...;
       range.pfn_shift = ...;
-      hmm_range_register(&range);
+      hmm_range_register(&range, mirror);
 
       /*
        * Just wait for range to be valid, safe to ignore return value as we
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index f0821638bbc6..71d6e7087b0b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -818,8 +818,11 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 				0 : range->flags[HMM_PFN_WRITE];
 	range->pfn_flags_mask = 0;
 	range->pfns = pfns;
-	hmm_range_register(range, mirror, start,
-			   start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);
+	range->page_shift = PAGE_SHIFT;
+	range->start = start;
+	range->end = start + ttm->num_pages * PAGE_SIZE;
+
+	hmm_range_register(range, mirror);
 
 	/*
 	 * Just wait for range to be valid, safe to ignore return value as we
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index b889d5ec4c7e..40e706234554 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -492,9 +492,7 @@ nouveau_range_fault(struct nouveau_svmm *svmm, struct hmm_range *range)
 	range->default_flags = 0;
 	range->pfn_flags_mask = -1UL;
 
-	ret = hmm_range_register(range, &svmm->mirror,
-				 range->start, range->end,
-				 PAGE_SHIFT);
+	ret = hmm_range_register(range, &svmm->mirror);
 	if (ret) {
 		up_read(&range->hmm->mm->mmap_sem);
 		return (int)ret;
@@ -682,6 +680,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
 			 args.i.p.addr + args.i.p.size, fn - fi);
 
 		/* Have HMM fault pages within the fault window to the GPU. */
+		range.page_shift = PAGE_SHIFT;
 		range.start = args.i.p.addr;
 		range.end = args.i.p.addr + args.i.p.size;
 		range.pfns = args.phys;
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 59be0aa2476d..c5b51376b453 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -400,11 +400,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror);
 /*
  * Please see Documentation/vm/hmm.rst for how to use the range API.
  */
-int hmm_range_register(struct hmm_range *range,
-		       struct hmm_mirror *mirror,
-		       unsigned long start,
-		       unsigned long end,
-		       unsigned page_shift);
+int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror);
 void hmm_range_unregister(struct hmm_range *range);
 
 /*
diff --git a/mm/hmm.c b/mm/hmm.c
index 3a3852660757..926735a3aef9 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -843,35 +843,25 @@ static void hmm_pfns_clear(struct hmm_range *range,
  * hmm_range_register() - start tracking change to CPU page table over a range
  * @range: range
  * @mm: the mm struct for the range of virtual address
- * @start: start virtual address (inclusive)
- * @end: end virtual address (exclusive)
- * @page_shift: expect page shift for the range
+ *
  * Return: 0 on success, -EFAULT if the address space is no longer valid
  *
  * Track updates to the CPU page table see include/linux/hmm.h
  */
-int hmm_range_register(struct hmm_range *range,
-		       struct hmm_mirror *mirror,
-		       unsigned long start,
-		       unsigned long end,
-		       unsigned page_shift)
+int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
 {
-	unsigned long mask = ((1UL << page_shift) - 1UL);
+	unsigned long mask = ((1UL << range->page_shift) - 1UL);
 	struct hmm *hmm = mirror->hmm;
 	unsigned long flags;
 
 	range->valid = false;
 	range->hmm = NULL;
 
-	if ((start & mask) || (end & mask))
+	if ((range->start & mask) || (range->end & mask))
 		return -EINVAL;
-	if (start >= end)
+	if (range->start >= range->end)
 		return -EINVAL;
 
-	range->page_shift = page_shift;
-	range->start = start;
-	range->end = end;
-
 	/* Prevent hmm_release() from running while the range is valid */
 	if (!mmget_not_zero(hmm->mm))
 		return -EFAULT;
-- 
2.20.1

[PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Christoph Hellwig]

All users pass PAGE_SIZE here, and if we wanted to support single
entries for huge pages we should really just add a HMM_FAULT_HUGEPAGE
flag instead that uses the huge page size instead of having the
caller calculate that size once, just for the hmm code to verify it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  1 -
 drivers/gpu/drm/nouveau/nouveau_svm.c   |  1 -
 include/linux/hmm.h                     | 22 -------------
 mm/hmm.c                                | 42 ++++++-------------------
 4 files changed, 9 insertions(+), 57 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 71d6e7087b0b..8bf79288c4e2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -818,7 +818,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 				0 : range->flags[HMM_PFN_WRITE];
 	range->pfn_flags_mask = 0;
 	range->pfns = pfns;
-	range->page_shift = PAGE_SHIFT;
 	range->start = start;
 	range->end = start + ttm->num_pages * PAGE_SIZE;
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index 40e706234554..e7068ce46949 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -680,7 +680,6 @@ nouveau_svm_fault(struct nvif_notify *notify)
 			 args.i.p.addr + args.i.p.size, fn - fi);
 
 		/* Have HMM fault pages within the fault window to the GPU. */
-		range.page_shift = PAGE_SHIFT;
 		range.start = args.i.p.addr;
 		range.end = args.i.p.addr + args.i.p.size;
 		range.pfns = args.phys;
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index c5b51376b453..51e18fbb8953 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -158,7 +158,6 @@ enum hmm_pfn_value_e {
  * @values: pfn value for some special case (none, special, error, ...)
  * @default_flags: default flags for the range (write, read, ... see hmm doc)
  * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
- * @page_shift: device virtual address shift value (should be >= PAGE_SHIFT)
  * @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
  * @valid: pfns array did not change since it has been fill by an HMM function
  */
@@ -172,31 +171,10 @@ struct hmm_range {
 	const uint64_t		*values;
 	uint64_t		default_flags;
 	uint64_t		pfn_flags_mask;
-	uint8_t			page_shift;
 	uint8_t			pfn_shift;
 	bool			valid;
 };
 
-/*
- * hmm_range_page_shift() - return the page shift for the range
- * @range: range being queried
- * Return: page shift (page size = 1 << page shift) for the range
- */
-static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
-{
-	return range->page_shift;
-}
-
-/*
- * hmm_range_page_size() - return the page size for the range
- * @range: range being queried
- * Return: page size for the range in bytes
- */
-static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
-{
-	return 1UL << hmm_range_page_shift(range);
-}
-
 /*
  * hmm_range_wait_until_valid() - wait for range to be valid
  * @range: range affected by invalidation to wait on
diff --git a/mm/hmm.c b/mm/hmm.c
index 926735a3aef9..f26d6abc4ed2 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -344,13 +344,12 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	uint64_t *pfns = range->pfns;
-	unsigned long i, page_size;
+	unsigned long i;
 
 	hmm_vma_walk->last = addr;
-	page_size = hmm_range_page_size(range);
-	i = (addr - range->start) >> range->page_shift;
+	i = (addr - range->start) >> PAGE_SHIFT;
 
-	for (; addr < end; addr += page_size, i++) {
+	for (; addr < end; addr += PAGE_SIZE, i++) {
 		pfns[i] = range->values[HMM_PFN_NONE];
 		if (fault || write_fault) {
 			int ret;
@@ -772,7 +771,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				      struct mm_walk *walk)
 {
 #ifdef CONFIG_HUGETLB_PAGE
-	unsigned long addr = start, i, pfn, mask, size, pfn_inc;
+	unsigned long addr = start, i, pfn, mask;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
@@ -783,24 +782,12 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 	pte_t entry;
 	int ret = 0;
 
-	size = huge_page_size(h);
-	mask = size - 1;
-	if (range->page_shift != PAGE_SHIFT) {
-		/* Make sure we are looking at a full page. */
-		if (start & mask)
-			return -EINVAL;
-		if (end < (start + size))
-			return -EINVAL;
-		pfn_inc = size >> PAGE_SHIFT;
-	} else {
-		pfn_inc = 1;
-		size = PAGE_SIZE;
-	}
+	mask = huge_page_size(h) - 1;
 
 	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
 	entry = huge_ptep_get(pte);
 
-	i = (start - range->start) >> range->page_shift;
+	i = (start - range->start) >> PAGE_SHIFT;
 	orig_pfn = range->pfns[i];
 	range->pfns[i] = range->values[HMM_PFN_NONE];
 	cpu_flags = pte_to_hmm_pfn_flags(range, entry);
@@ -812,8 +799,8 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 		goto unlock;
 	}
 
-	pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
-	for (; addr < end; addr += size, i++, pfn += pfn_inc)
+	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
+	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;
@@ -850,14 +837,13 @@ static void hmm_pfns_clear(struct hmm_range *range,
  */
 int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
 {
-	unsigned long mask = ((1UL << range->page_shift) - 1UL);
 	struct hmm *hmm = mirror->hmm;
 	unsigned long flags;
 
 	range->valid = false;
 	range->hmm = NULL;
 
-	if ((range->start & mask) || (range->end & mask))
+	if ((range->start & (PAGE_SIZE - 1)) || (range->end & (PAGE_SIZE - 1)))
 		return -EINVAL;
 	if (range->start >= range->end)
 		return -EINVAL;
@@ -964,16 +950,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 		if (vma == NULL || (vma->vm_flags & device_vma))
 			return -EFAULT;
 
-		if (is_vm_hugetlb_page(vma)) {
-			if (huge_page_shift(hstate_vma(vma)) !=
-			    range->page_shift &&
-			    range->page_shift != PAGE_SHIFT)
-				return -EINVAL;
-		} else {
-			if (range->page_shift != PAGE_SHIFT)
-				return -EINVAL;
-		}
-
 		if (!(vma->vm_flags & VM_READ)) {
 			/*
 			 * If vma do not allow read access, then assume that it
-- 
2.20.1

[PATCH 08/13] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry

[Christoph Hellwig]

The pagewalk code already passes the value as the hmask parameter.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index f26d6abc4ed2..88b77a4a6a1e 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				      struct mm_walk *walk)
 {
 #ifdef CONFIG_HUGETLB_PAGE
-	unsigned long addr = start, i, pfn, mask;
+	unsigned long addr = start, i, pfn;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
-	struct hstate *h = hstate_vma(vma);
 	uint64_t orig_pfn, cpu_flags;
 	bool fault, write_fault;
 	spinlock_t *ptl;
 	pte_t entry;
 	int ret = 0;
 
-	mask = huge_page_size(h) - 1;
-
 	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
 	entry = huge_ptep_get(pte);
 
@@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 		goto unlock;
 	}
 
-	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
+	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);
 	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
 		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 				 cpu_flags;
-- 
2.20.1

[PATCH 09/13] mm: don't abuse pte_index() in hmm_vma_handle_pmd

[Christoph Hellwig]

pte_index is an internal arch helper in various architectures,
without consistent semantics.  Open code that calculation of a PMD
index based on the virtual address instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 88b77a4a6a1e..e63ab7f11334 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -486,7 +486,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 	if (pmd_protnone(pmd) || fault || write_fault)
 		return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 
-	pfn = pmd_pfn(pmd) + pte_index(addr);
+	pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
 		if (pmd_devmap(pmd)) {
 			pgmap = get_dev_pagemap(pfn, pgmap);
-- 
2.20.1

[PATCH 10/13] mm: only define hmm_vma_walk_pud if needed

[Christoph Hellwig]

We only need the special pud_entry walker if PUD-sized hugepages and
pte mappings are supported, else the common pagewalk code will take
care of the iteration.  Not implementing this callback reduced the
amount of code compiled for non-x86 platforms, and also fixes compile
failures with other architectures when helpers like pud_pfn are not
implemented.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index e63ab7f11334..4d3bd41b6522 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -455,15 +455,6 @@ static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 				range->flags[HMM_PFN_VALID];
 }
 
-static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
-{
-	if (!pud_present(pud))
-		return 0;
-	return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
-				range->flags[HMM_PFN_WRITE] :
-				range->flags[HMM_PFN_VALID];
-}
-
 static int hmm_vma_handle_pmd(struct mm_walk *walk,
 			      unsigned long addr,
 			      unsigned long end,
@@ -700,10 +691,19 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 	return 0;
 }
 
-static int hmm_vma_walk_pud(pud_t *pudp,
-			    unsigned long start,
-			    unsigned long end,
-			    struct mm_walk *walk)
+#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
+    defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
+static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
+{
+	if (!pud_present(pud))
+		return 0;
+	return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
+				range->flags[HMM_PFN_WRITE] :
+				range->flags[HMM_PFN_VALID];
+}
+
+static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
+		struct mm_walk *walk)
 {
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
@@ -765,6 +765,9 @@ static int hmm_vma_walk_pud(pud_t *pudp,
 
 	return 0;
 }
+#else
+#define hmm_vma_walk_pud	NULL
+#endif
 
 static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				      unsigned long start, unsigned long end,
-- 
2.20.1

[PATCH 11/13] mm: cleanup the hmm_vma_handle_pmd stub

[Christoph Hellwig]

Stub out the whole function when CONFIG_TRANSPARENT_HUGEPAGE is not set
to make the function easier to read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 4d3bd41b6522..f4e90ea5779f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -455,13 +455,10 @@ static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
 				range->flags[HMM_PFN_VALID];
 }
 
-static int hmm_vma_handle_pmd(struct mm_walk *walk,
-			      unsigned long addr,
-			      unsigned long end,
-			      uint64_t *pfns,
-			      pmd_t pmd)
-{
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
+		unsigned long end, uint64_t *pfns, pmd_t pmd)
+{
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct dev_pagemap *pgmap = NULL;
@@ -490,11 +487,14 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 		put_dev_pagemap(pgmap);
 	hmm_vma_walk->last = end;
 	return 0;
-#else
-	/* If THP is not enabled then we should never reach this code ! */
+}
+#else /* CONFIG_TRANSPARENT_HUGEPAGE */
+static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
+		unsigned long end, uint64_t *pfns, pmd_t pmd)
+{
 	return -EINVAL;
-#endif
 }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 {
-- 
2.20.1

[PATCH 12/13] mm: cleanup the hmm_vma_walk_hugetlb_entry stub

[Christoph Hellwig]

Stub out the whole function and assign NULL to the .hugetlb_entry method
if CONFIG_HUGETLB_PAGE is not set, as the method won't ever be called in
that case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index f4e90ea5779f..2b56a4af1001 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -769,11 +769,11 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 #define hmm_vma_walk_pud	NULL
 #endif
 
+#ifdef CONFIG_HUGETLB_PAGE
 static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				      unsigned long start, unsigned long end,
 				      struct mm_walk *walk)
 {
-#ifdef CONFIG_HUGETLB_PAGE
 	unsigned long addr = start, i, pfn;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
@@ -812,10 +812,10 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 		return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 
 	return ret;
-#else /* CONFIG_HUGETLB_PAGE */
-	return -EINVAL;
-#endif
 }
+#else
+#define hmm_vma_walk_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
 
 static void hmm_pfns_clear(struct hmm_range *range,
 			   uint64_t *pfns,
-- 
2.20.1

[PATCH 13/13] mm: allow HMM_MIRROR on all architectures with MMU

[Christoph Hellwig]

There isn't really any architecture specific code in this page table
walk implementation, so drop the dependencies.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/Kconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 56cec636a1fc..b18782be969c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -677,8 +677,7 @@ config DEV_PAGEMAP_OPS
 
 config HMM_MIRROR
 	bool "HMM mirror CPU page table into a device page table"
-	depends on (X86_64 || PPC64)
-	depends on MMU && 64BIT
+	depends on MMU
 	select MMU_NOTIFIER
 	help
 	  Select HMM_MIRROR if you want to mirror range of the CPU page table of a
-- 
2.20.1

Re: [PATCH 01/13] amdgpu: remove -EAGAIN handling for hmm_range_fault

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:51AM +0300, Christoph Hellwig wrote:
> hmm_range_fault can only return -EAGAIN if called with the block
> argument set to false, so remove the special handling for it.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 23 +++--------------------
>  1 file changed, 3 insertions(+), 20 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Jason

Re: [PATCH 02/13] amdgpu: don't initialize range->list in amdgpu_hmm_init_range

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:52AM +0300, Christoph Hellwig wrote:
> The list is used to add the range to another list as an entry in the
> core hmm code, so there is no need to initialize it in a driver.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c | 1 -
>  1 file changed, 1 deletion(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Jason

Re: [PATCH 03/13] nouveau: pass struct nouveau_svmm to nouveau_range_fault

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:53AM +0300, Christoph Hellwig wrote:
> This avoid having to abuse the vma field in struct hmm_range to unlock
> the mmap_sem.

I think the change inside hmm_range_fault got lost on rebase, it is
now using:

                up_read(&range->hmm->mm->mmap_sem);

But, yes, lets change it to use svmm->mm and try to keep struct hmm
opaque to drivers

Jason

Re: [PATCH 05/13] mm: remove the unused vma argument to hmm_range_dma_unmap

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:55AM +0300, Christoph Hellwig wrote:
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  include/linux/hmm.h | 1 -
>  mm/hmm.c            | 2 --
>  2 files changed, 3 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Unclear what this was intended for, but I think if we need to carry
information from the dma_map to unmap it should be done in some opaque
way.

The driver should not have to care about VMAs, beyond perhaps using
VMAs to guide what VA ranges to mirror.

Jason

Re: [PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:57AM +0300, Christoph Hellwig wrote:
> All users pass PAGE_SIZE here, and if we wanted to support single
> entries for huge pages we should really just add a HMM_FAULT_HUGEPAGE
> flag instead that uses the huge page size instead of having the
> caller calculate that size once, just for the hmm code to verify it.

I suspect this was added for the ODP conversion that does use both
page sizes. I think the ODP code for this is kind of broken, but I
haven't delved into that..

The challenge is that the driver needs to know what page size to
configure the hardware before it does any range stuff.

The other challenge is that the HW is configured to do only one page
size, and if the underlying CPU page side changes it goes south.

What I would prefer is if the driver could somehow dynamically adjust
the the page size after each dma map, but I don't know if ODP HW can
do that.

Since this is all driving toward making ODP use this maybe we should
keep this API? 

I'm not sure I can loose the crappy huge page support in ODP.

Jason

Re: [PATCH 03/13] nouveau: pass struct nouveau_svmm to nouveau_range_fault

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 12:35:59PM +0000, Jason Gunthorpe wrote:
> On Tue, Jul 30, 2019 at 08:51:53AM +0300, Christoph Hellwig wrote:
> > This avoid having to abuse the vma field in struct hmm_range to unlock
> > the mmap_sem.
> 
> I think the change inside hmm_range_fault got lost on rebase, it is
> now using:
> 
>                 up_read(&range->hmm->mm->mmap_sem);
> 
> But, yes, lets change it to use svmm->mm and try to keep struct hmm
> opaque to drivers

It got lost somewhat intentionally as I didn't want the churn, but I
forgot to update the changelog.  But if you are fine with changing it
over I can bring it back.

Re: [PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 12:55:17PM +0000, Jason Gunthorpe wrote:
> I suspect this was added for the ODP conversion that does use both
> page sizes. I think the ODP code for this is kind of broken, but I
> haven't delved into that..
> 
> The challenge is that the driver needs to know what page size to
> configure the hardware before it does any range stuff.
> 
> The other challenge is that the HW is configured to do only one page
> size, and if the underlying CPU page side changes it goes south.
> 
> What I would prefer is if the driver could somehow dynamically adjust
> the the page size after each dma map, but I don't know if ODP HW can
> do that.
> 
> Since this is all driving toward making ODP use this maybe we should
> keep this API? 
> 
> I'm not sure I can loose the crappy huge page support in ODP.

The problem is that I see no way how to use the current API.  To know
the huge page size you need to have the vma, and the current API
doesn't require a vma to be passed in.

That's why I suggested an api where we pass in a flag that huge pages
are ok into hmm_range_fault, and it then could pass the shift out, and
limits itself to a single vma (which it normally doesn't, that is an
additional complication).  But all this seems really awkward in terms
of an API still.  AFAIK ODP is only used by mlx5, and mlx5 unlike other
IB HCAs can use scatterlist style MRs with variable length per entry,
so even if we pass multiple pages per entry from hmm it could coalesce
them.  The best API for mlx4 would of course be to pass a biovec-style
variable length structure that hmm_fault could fill out, but that would
be a major restructure.

Re: [PATCH 03/13] nouveau: pass struct nouveau_svmm to nouveau_range_fault

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 03:10:38PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 30, 2019 at 12:35:59PM +0000, Jason Gunthorpe wrote:
> > On Tue, Jul 30, 2019 at 08:51:53AM +0300, Christoph Hellwig wrote:
> > > This avoid having to abuse the vma field in struct hmm_range to unlock
> > > the mmap_sem.
> > 
> > I think the change inside hmm_range_fault got lost on rebase, it is
> > now using:
> > 
> >                 up_read(&range->hmm->mm->mmap_sem);
> > 
> > But, yes, lets change it to use svmm->mm and try to keep struct hmm
> > opaque to drivers
> 
> It got lost somewhat intentionally as I didn't want the churn, but I
> forgot to update the changelog.  But if you are fine with changing it
> over I can bring it back.

I have a patch deleting hmm->mm, so using svmm seems cleaner churn
here, we could defer and I can fold this into that patch?

Jason

Re: [PATCH 03/13] nouveau: pass struct nouveau_svmm to nouveau_range_fault

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 01:14:58PM +0000, Jason Gunthorpe wrote:
> I have a patch deleting hmm->mm, so using svmm seems cleaner churn
> here, we could defer and I can fold this into that patch?

Sounds good.  If I don't need to resend feel fee to fold it, otherwise
I'll fix it up.

Re: [PATCH 08/13] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:58AM +0300, Christoph Hellwig wrote:
> The pagewalk code already passes the value as the hmask parameter.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  mm/hmm.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f26d6abc4ed2..88b77a4a6a1e 100644
> +++ b/mm/hmm.c
> @@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  				      struct mm_walk *walk)
>  {
>  #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask;
> +	unsigned long addr = start, i, pfn;
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
>  	struct vm_area_struct *vma = walk->vma;
> -	struct hstate *h = hstate_vma(vma);
>  	uint64_t orig_pfn, cpu_flags;
>  	bool fault, write_fault;
>  	spinlock_t *ptl;
>  	pte_t entry;
>  	int ret = 0;
>  
> -	mask = huge_page_size(h) - 1;
> -
>  	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>  	entry = huge_ptep_get(pte);
>  
> @@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  		goto unlock;
>  	}
>  
> -	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);

I don't know this hstate stuff, but this doesn't look the same?

static int walk_hugetlb_range(unsigned long addr, unsigned long end, {
        struct hstate *h = hstate_vma(vma);
        unsigned long hmask = huge_page_mask(h); // aka h->mask

                        err = walk->hugetlb_entry(pte, hmask, addr, next, walk);

And the first place I found setting h->mask is:

void __init hugetlb_add_hstate(unsigned int order) {
	h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);

Compared with
    mask = huge_page_size(h) - 1;
         = ((unsigned long)PAGE_SIZE << h->order) - 1

Looks like hmask == ~mask

?

Jason

Re: [PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 03:14:30PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 30, 2019 at 12:55:17PM +0000, Jason Gunthorpe wrote:
> > I suspect this was added for the ODP conversion that does use both
> > page sizes. I think the ODP code for this is kind of broken, but I
> > haven't delved into that..
> > 
> > The challenge is that the driver needs to know what page size to
> > configure the hardware before it does any range stuff.
> > 
> > The other challenge is that the HW is configured to do only one page
> > size, and if the underlying CPU page side changes it goes south.
> > 
> > What I would prefer is if the driver could somehow dynamically adjust
> > the the page size after each dma map, but I don't know if ODP HW can
> > do that.
> > 
> > Since this is all driving toward making ODP use this maybe we should
> > keep this API? 
> > 
> > I'm not sure I can loose the crappy huge page support in ODP.
> 
> The problem is that I see no way how to use the current API.  To know
> the huge page size you need to have the vma, and the current API
> doesn't require a vma to be passed in.

The way ODP seems to work is once in hugetlb mode the dma addresses
must give huge pages or the page fault will be failed. I think that is
a terrible design, but this is how the driver is ..

So, from this HMM perspective if the caller asked for huge pages then
the results have to be all huge pages or a hard failure.

It is not negotiated as an optimization like you are thinking.

[note, I haven't yet checked carefully how this works in ODP, every
 time I look at parts of it the thing seems crazy]

> That's why I suggested an api where we pass in a flag that huge pages
> are ok into hmm_range_fault, and it then could pass the shift out, and
> limits itself to a single vma (which it normally doesn't, that is an
> additional complication).  But all this seems really awkward in terms
> of an API still.  AFAIK ODP is only used by mlx5, and mlx5 unlike other
> IB HCAs can use scatterlist style MRs with variable length per entry,
> so even if we pass multiple pages per entry from hmm it could coalesce
> them.  

When the driver takes faults it has to repair the MR mapping, and
fixing a page in the middle of a variable length SGL would be pretty
complicated. Even so, I don't think the SG_GAPs feature and ODP are
compatible - I'm pretty sure ODP has to be page lists not SGL..

However, what ODP can maybe do is represent a full multi-level page
table, so we could have 2M entries that map to a single DMA or to
another page table w/ 4k pages (have to check on this)

But the driver isn't set up to do that right now.

> The best API for mlx4 would of course be to pass a biovec-style
> variable length structure that hmm_fault could fill out, but that would
> be a major restructure.

It would work, but the driver has to expand that into a page list
right awayhow.

We can't even dma map the biovec with today's dma API as it needs the
ability to remap on a page granularity.

Jason

Re: [PATCH 06/13] mm: remove superflous arguments from hmm_range_register

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:51:56AM +0300, Christoph Hellwig wrote:
> The start, end and page_shift values are all saved in the range
> structure, so we might as well use that for argument passing.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  Documentation/vm/hmm.rst                |  2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  7 +++++--
>  drivers/gpu/drm/nouveau/nouveau_svm.c   |  5 ++---
>  include/linux/hmm.h                     |  6 +-----
>  mm/hmm.c                                | 20 +++++---------------
>  5 files changed, 14 insertions(+), 26 deletions(-)

I also don't really like how the API sets up some things in the struct
and some things via arguments, so:

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Jason

Re: [PATCH 11/13] mm: cleanup the hmm_vma_handle_pmd stub

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:52:01AM +0300, Christoph Hellwig wrote:
> Stub out the whole function when CONFIG_TRANSPARENT_HUGEPAGE is not set
> to make the function easier to read.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  mm/hmm.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 4d3bd41b6522..f4e90ea5779f 100644
> +++ b/mm/hmm.c
> @@ -455,13 +455,10 @@ static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
>  				range->flags[HMM_PFN_VALID];
>  }
>  
> -static int hmm_vma_handle_pmd(struct mm_walk *walk,
> -			      unsigned long addr,
> -			      unsigned long end,
> -			      uint64_t *pfns,
> -			      pmd_t pmd)
> -{
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
> +		unsigned long end, uint64_t *pfns, pmd_t pmd)
> +{
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
>  	struct dev_pagemap *pgmap = NULL;
> @@ -490,11 +487,14 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
>  		put_dev_pagemap(pgmap);
>  	hmm_vma_walk->last = end;
>  	return 0;
> -#else
> -	/* If THP is not enabled then we should never reach this 

This old comment says we should never get here

> +}
> +#else /* CONFIG_TRANSPARENT_HUGEPAGE */
> +static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
> +		unsigned long end, uint64_t *pfns, pmd_t pmd)
> +{
>  	return -EINVAL;

So could we just do
   #define hmm_vma_handle_pmd NULL

?

At the very least this seems like a WARN_ON too?

Jason

Re: [PATCH 10/13] mm: only define hmm_vma_walk_pud if needed

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:52:00AM +0300, Christoph Hellwig wrote:
> We only need the special pud_entry walker if PUD-sized hugepages and
> pte mappings are supported, else the common pagewalk code will take
> care of the iteration.  Not implementing this callback reduced the
> amount of code compiled for non-x86 platforms, and also fixes compile
> failures with other architectures when helpers like pud_pfn are not
> implemented.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  mm/hmm.c | 29 ++++++++++++++++-------------
>  1 file changed, 16 insertions(+), 13 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Jason

Re: [PATCH 12/13] mm: cleanup the hmm_vma_walk_hugetlb_entry stub

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:52:02AM +0300, Christoph Hellwig wrote:
> Stub out the whole function and assign NULL to the .hugetlb_entry method
> if CONFIG_HUGETLB_PAGE is not set, as the method won't ever be called in
> that case.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  mm/hmm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Jason

Re: [PATCH 13/13] mm: allow HMM_MIRROR on all architectures with MMU

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 08:52:03AM +0300, Christoph Hellwig wrote:
> There isn't really any architecture specific code in this page table
> walk implementation, so drop the dependencies.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  mm/Kconfig | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

Happy to see it, lets try to get this patch + the required parts of
this series into linux-next to be really sure

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Thanks,
Jason

Re: [PATCH 13/13] mm: allow HMM_MIRROR on all architectures with MMU

[Jason Gunthorpe]

On Tue, Jul 30, 2019 at 03:03:46PM -0300, Jason Gunthorpe wrote:
> On Tue, Jul 30, 2019 at 08:52:03AM +0300, Christoph Hellwig wrote:
> > There isn't really any architecture specific code in this page table
> > walk implementation, so drop the dependencies.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> >  mm/Kconfig | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> Happy to see it, lets try to get this patch + the required parts of
> this series into linux-next to be really sure
> 
> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Oh, can we make this into a non-user selectable option now? 

ie have the drivers that use the API select it?

Thanks,
Jason

Re: [PATCH 08/13] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry

[Ralph Campbell]

On 7/29/19 10:51 PM, Christoph Hellwig wrote:
> The pagewalk code already passes the value as the hmask parameter.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   mm/hmm.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f26d6abc4ed2..88b77a4a6a1e 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   				      struct mm_walk *walk)
>   {
>   #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask;
> +	unsigned long addr = start, i, pfn;
>   	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>   	struct hmm_range *range = hmm_vma_walk->range;
>   	struct vm_area_struct *vma = walk->vma;
> -	struct hstate *h = hstate_vma(vma);
>   	uint64_t orig_pfn, cpu_flags;
>   	bool fault, write_fault;
>   	spinlock_t *ptl;
>   	pte_t entry;
>   	int ret = 0;
>   
> -	mask = huge_page_size(h) - 1;
> -
>   	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>   	entry = huge_ptep_get(pte);
>   
> @@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   		goto unlock;
>   	}
>   
> -	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);

This needs to be "~hmask" so that the upper bits of the start address
are not added to the pfn. It's the middle bits of the address that
offset into the huge page that are needed.

>   	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
>   		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
>   				 cpu_flags;
> 

Re: [PATCH 01/13] amdgpu: remove -EAGAIN handling for hmm_range_fault

[Kuehling, Felix]

On 2019-07-30 1:51 a.m., Christoph Hellwig wrote:
> hmm_range_fault can only return -EAGAIN if called with the block
> argument set to false, so remove the special handling for it.

The block argument no longer exists. You replaced that with the 
HMM_FAULT_ALLOW_RETRY with opposite logic. So this should read 
"hmm_range_fault can only return -EAGAIN if called with the 
HMM_FAULT_ALLOW_RETRY flag set, so remove the special handling for it.

With that fixed, this commit is Reviewed-by: Felix Kuehling 
<Felix.Kuehling@amd.com>

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 23 +++--------------------
>   1 file changed, 3 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 12a59ac83f72..f0821638bbc6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -778,7 +778,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   	struct hmm_range *range;
>   	unsigned long i;
>   	uint64_t *pfns;
> -	int retry = 0;
>   	int r = 0;
>   
>   	if (!mm) /* Happens during process shutdown */
> @@ -822,7 +821,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   	hmm_range_register(range, mirror, start,
>   			   start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);
>   
> -retry:
>   	/*
>   	 * Just wait for range to be valid, safe to ignore return value as we
>   	 * will use the return value of hmm_range_fault() below under the
> @@ -831,24 +829,12 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   	hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT);
>   
>   	down_read(&mm->mmap_sem);
> -
>   	r = hmm_range_fault(range, 0);
> -	if (unlikely(r < 0)) {
> -		if (likely(r == -EAGAIN)) {
> -			/*
> -			 * return -EAGAIN, mmap_sem is dropped
> -			 */
> -			if (retry++ < MAX_RETRY_HMM_RANGE_FAULT)
> -				goto retry;
> -			else
> -				pr_err("Retry hmm fault too many times\n");
> -		}
> -
> -		goto out_up_read;
> -	}
> -
>   	up_read(&mm->mmap_sem);
>   
> +	if (unlikely(r < 0))
> +		goto out_free_pfns;
> +
>   	for (i = 0; i < ttm->num_pages; i++) {
>   		pages[i] = hmm_device_entry_to_page(range, pfns[i]);
>   		if (unlikely(!pages[i])) {
> @@ -864,9 +850,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   
>   	return 0;
>   
> -out_up_read:
> -	if (likely(r != -EAGAIN))
> -		up_read(&mm->mmap_sem);
>   out_free_pfns:
>   	hmm_range_unregister(range);
>   	kvfree(pfns);

Re: [PATCH 02/13] amdgpu: don't initialize range->list in amdgpu_hmm_init_range

[Kuehling, Felix]

On 2019-07-30 1:51 a.m., Christoph Hellwig wrote:
> The list is used to add the range to another list as an entry in the
> core hmm code, so there is no need to initialize it in a driver.

I've seen code that uses list_empty to check whether a list head has 
been added to a list or not. For that to work, the list head needs to be 
initialized, and it has to be removed with list_del_init. If HMM doesn't 
ever do that with range->list, then this patch is Reviewed-by: Felix 
Kuehling <Felix.Kuehling@amd.com>


>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> index b698b423b25d..60b9fc9561d7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> @@ -484,6 +484,5 @@ void amdgpu_hmm_init_range(struct hmm_range *range)
>   		range->flags = hmm_range_flags;
>   		range->values = hmm_range_values;
>   		range->pfn_shift = PAGE_SHIFT;
> -		INIT_LIST_HEAD(&range->list);
>   	}
>   }

Re: [PATCH 06/13] mm: remove superflous arguments from hmm_range_register

[Kuehling, Felix]

On 2019-07-30 1:51 a.m., Christoph Hellwig wrote:
> The start, end and page_shift values are all saved in the range
> structure, so we might as well use that for argument passing.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>


> ---
>   Documentation/vm/hmm.rst                |  2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  7 +++++--
>   drivers/gpu/drm/nouveau/nouveau_svm.c   |  5 ++---
>   include/linux/hmm.h                     |  6 +-----
>   mm/hmm.c                                | 20 +++++---------------
>   5 files changed, 14 insertions(+), 26 deletions(-)
>
> diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
> index ddcb5ca8b296..e63c11f7e0e0 100644
> --- a/Documentation/vm/hmm.rst
> +++ b/Documentation/vm/hmm.rst
> @@ -222,7 +222,7 @@ The usage pattern is::
>         range.flags = ...;
>         range.values = ...;
>         range.pfn_shift = ...;
> -      hmm_range_register(&range);
> +      hmm_range_register(&range, mirror);
>   
>         /*
>          * Just wait for range to be valid, safe to ignore return value as we
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index f0821638bbc6..71d6e7087b0b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -818,8 +818,11 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   				0 : range->flags[HMM_PFN_WRITE];
>   	range->pfn_flags_mask = 0;
>   	range->pfns = pfns;
> -	hmm_range_register(range, mirror, start,
> -			   start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);
> +	range->page_shift = PAGE_SHIFT;
> +	range->start = start;
> +	range->end = start + ttm->num_pages * PAGE_SIZE;
> +
> +	hmm_range_register(range, mirror);
>   
>   	/*
>   	 * Just wait for range to be valid, safe to ignore return value as we
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index b889d5ec4c7e..40e706234554 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -492,9 +492,7 @@ nouveau_range_fault(struct nouveau_svmm *svmm, struct hmm_range *range)
>   	range->default_flags = 0;
>   	range->pfn_flags_mask = -1UL;
>   
> -	ret = hmm_range_register(range, &svmm->mirror,
> -				 range->start, range->end,
> -				 PAGE_SHIFT);
> +	ret = hmm_range_register(range, &svmm->mirror);
>   	if (ret) {
>   		up_read(&range->hmm->mm->mmap_sem);
>   		return (int)ret;
> @@ -682,6 +680,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
>   			 args.i.p.addr + args.i.p.size, fn - fi);
>   
>   		/* Have HMM fault pages within the fault window to the GPU. */
> +		range.page_shift = PAGE_SHIFT;
>   		range.start = args.i.p.addr;
>   		range.end = args.i.p.addr + args.i.p.size;
>   		range.pfns = args.phys;
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 59be0aa2476d..c5b51376b453 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -400,11 +400,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror);
>   /*
>    * Please see Documentation/vm/hmm.rst for how to use the range API.
>    */
> -int hmm_range_register(struct hmm_range *range,
> -		       struct hmm_mirror *mirror,
> -		       unsigned long start,
> -		       unsigned long end,
> -		       unsigned page_shift);
> +int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror);
>   void hmm_range_unregister(struct hmm_range *range);
>   
>   /*
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 3a3852660757..926735a3aef9 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -843,35 +843,25 @@ static void hmm_pfns_clear(struct hmm_range *range,
>    * hmm_range_register() - start tracking change to CPU page table over a range
>    * @range: range
>    * @mm: the mm struct for the range of virtual address
> - * @start: start virtual address (inclusive)
> - * @end: end virtual address (exclusive)
> - * @page_shift: expect page shift for the range
> + *
>    * Return: 0 on success, -EFAULT if the address space is no longer valid
>    *
>    * Track updates to the CPU page table see include/linux/hmm.h
>    */
> -int hmm_range_register(struct hmm_range *range,
> -		       struct hmm_mirror *mirror,
> -		       unsigned long start,
> -		       unsigned long end,
> -		       unsigned page_shift)
> +int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
>   {
> -	unsigned long mask = ((1UL << page_shift) - 1UL);
> +	unsigned long mask = ((1UL << range->page_shift) - 1UL);
>   	struct hmm *hmm = mirror->hmm;
>   	unsigned long flags;
>   
>   	range->valid = false;
>   	range->hmm = NULL;
>   
> -	if ((start & mask) || (end & mask))
> +	if ((range->start & mask) || (range->end & mask))
>   		return -EINVAL;
> -	if (start >= end)
> +	if (range->start >= range->end)
>   		return -EINVAL;
>   
> -	range->page_shift = page_shift;
> -	range->start = start;
> -	range->end = end;
> -
>   	/* Prevent hmm_release() from running while the range is valid */
>   	if (!mmget_not_zero(hmm->mm))
>   		return -EFAULT;

Re: [PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Kuehling, Felix]

On 2019-07-30 1:51 a.m., Christoph Hellwig wrote:
> All users pass PAGE_SIZE here, and if we wanted to support single
> entries for huge pages we should really just add a HMM_FAULT_HUGEPAGE
> flag instead that uses the huge page size instead of having the
> caller calculate that size once, just for the hmm code to verify it.

Maybe this was meant to support device page size != native page size? 
Anyway, looks like we didn't use it that way.

Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>


>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  1 -
>   drivers/gpu/drm/nouveau/nouveau_svm.c   |  1 -
>   include/linux/hmm.h                     | 22 -------------
>   mm/hmm.c                                | 42 ++++++-------------------
>   4 files changed, 9 insertions(+), 57 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 71d6e7087b0b..8bf79288c4e2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -818,7 +818,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
>   				0 : range->flags[HMM_PFN_WRITE];
>   	range->pfn_flags_mask = 0;
>   	range->pfns = pfns;
> -	range->page_shift = PAGE_SHIFT;
>   	range->start = start;
>   	range->end = start + ttm->num_pages * PAGE_SIZE;
>   
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index 40e706234554..e7068ce46949 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -680,7 +680,6 @@ nouveau_svm_fault(struct nvif_notify *notify)
>   			 args.i.p.addr + args.i.p.size, fn - fi);
>   
>   		/* Have HMM fault pages within the fault window to the GPU. */
> -		range.page_shift = PAGE_SHIFT;
>   		range.start = args.i.p.addr;
>   		range.end = args.i.p.addr + args.i.p.size;
>   		range.pfns = args.phys;
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index c5b51376b453..51e18fbb8953 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -158,7 +158,6 @@ enum hmm_pfn_value_e {
>    * @values: pfn value for some special case (none, special, error, ...)
>    * @default_flags: default flags for the range (write, read, ... see hmm doc)
>    * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
> - * @page_shift: device virtual address shift value (should be >= PAGE_SHIFT)
>    * @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
>    * @valid: pfns array did not change since it has been fill by an HMM function
>    */
> @@ -172,31 +171,10 @@ struct hmm_range {
>   	const uint64_t		*values;
>   	uint64_t		default_flags;
>   	uint64_t		pfn_flags_mask;
> -	uint8_t			page_shift;
>   	uint8_t			pfn_shift;
>   	bool			valid;
>   };
>   
> -/*
> - * hmm_range_page_shift() - return the page shift for the range
> - * @range: range being queried
> - * Return: page shift (page size = 1 << page shift) for the range
> - */
> -static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
> -{
> -	return range->page_shift;
> -}
> -
> -/*
> - * hmm_range_page_size() - return the page size for the range
> - * @range: range being queried
> - * Return: page size for the range in bytes
> - */
> -static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
> -{
> -	return 1UL << hmm_range_page_shift(range);
> -}
> -
>   /*
>    * hmm_range_wait_until_valid() - wait for range to be valid
>    * @range: range affected by invalidation to wait on
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 926735a3aef9..f26d6abc4ed2 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -344,13 +344,12 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
>   	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>   	struct hmm_range *range = hmm_vma_walk->range;
>   	uint64_t *pfns = range->pfns;
> -	unsigned long i, page_size;
> +	unsigned long i;
>   
>   	hmm_vma_walk->last = addr;
> -	page_size = hmm_range_page_size(range);
> -	i = (addr - range->start) >> range->page_shift;
> +	i = (addr - range->start) >> PAGE_SHIFT;
>   
> -	for (; addr < end; addr += page_size, i++) {
> +	for (; addr < end; addr += PAGE_SIZE, i++) {
>   		pfns[i] = range->values[HMM_PFN_NONE];
>   		if (fault || write_fault) {
>   			int ret;
> @@ -772,7 +771,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   				      struct mm_walk *walk)
>   {
>   #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask, size, pfn_inc;
> +	unsigned long addr = start, i, pfn, mask;
>   	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>   	struct hmm_range *range = hmm_vma_walk->range;
>   	struct vm_area_struct *vma = walk->vma;
> @@ -783,24 +782,12 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   	pte_t entry;
>   	int ret = 0;
>   
> -	size = huge_page_size(h);
> -	mask = size - 1;
> -	if (range->page_shift != PAGE_SHIFT) {
> -		/* Make sure we are looking at a full page. */
> -		if (start & mask)
> -			return -EINVAL;
> -		if (end < (start + size))
> -			return -EINVAL;
> -		pfn_inc = size >> PAGE_SHIFT;
> -	} else {
> -		pfn_inc = 1;
> -		size = PAGE_SIZE;
> -	}
> +	mask = huge_page_size(h) - 1;
>   
>   	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>   	entry = huge_ptep_get(pte);
>   
> -	i = (start - range->start) >> range->page_shift;
> +	i = (start - range->start) >> PAGE_SHIFT;
>   	orig_pfn = range->pfns[i];
>   	range->pfns[i] = range->values[HMM_PFN_NONE];
>   	cpu_flags = pte_to_hmm_pfn_flags(range, entry);
> @@ -812,8 +799,8 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   		goto unlock;
>   	}
>   
> -	pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
> -	for (; addr < end; addr += size, i++, pfn += pfn_inc)
> +	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	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;
> @@ -850,14 +837,13 @@ static void hmm_pfns_clear(struct hmm_range *range,
>    */
>   int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
>   {
> -	unsigned long mask = ((1UL << range->page_shift) - 1UL);
>   	struct hmm *hmm = mirror->hmm;
>   	unsigned long flags;
>   
>   	range->valid = false;
>   	range->hmm = NULL;
>   
> -	if ((range->start & mask) || (range->end & mask))
> +	if ((range->start & (PAGE_SIZE - 1)) || (range->end & (PAGE_SIZE - 1)))
>   		return -EINVAL;
>   	if (range->start >= range->end)
>   		return -EINVAL;
> @@ -964,16 +950,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
>   		if (vma == NULL || (vma->vm_flags & device_vma))
>   			return -EFAULT;
>   
> -		if (is_vm_hugetlb_page(vma)) {
> -			if (huge_page_shift(hstate_vma(vma)) !=
> -			    range->page_shift &&
> -			    range->page_shift != PAGE_SHIFT)
> -				return -EINVAL;
> -		} else {
> -			if (range->page_shift != PAGE_SHIFT)
> -				return -EINVAL;
> -		}
> -
>   		if (!(vma->vm_flags & VM_READ)) {
>   			/*
>   			 * If vma do not allow read access, then assume that it

Re: [PATCH 02/13] amdgpu: don't initialize range->list in amdgpu_hmm_init_range

[Jason Gunthorpe]

On Wed, Jul 31, 2019 at 01:25:06PM +0000, Kuehling, Felix wrote:
> On 2019-07-30 1:51 a.m., Christoph Hellwig wrote:
> > The list is used to add the range to another list as an entry in the
> > core hmm code, so there is no need to initialize it in a driver.
> 
> I've seen code that uses list_empty to check whether a list head has 
> been added to a list or not. For that to work, the list head needs to be 
> initialized, and it has to be removed with list_del_init. 

I think the ida is that 'list' is a private member of range and
drivers shouldn't touch it at all.

> ever do that with range->list, then this patch is Reviewed-by: Felix 
> Kuehling <Felix.Kuehling@amd.com>

Please put tags on their own empty line so that patchworks will
collect them automatically..

Jason

Re: [PATCH 07/13] mm: remove the page_shift member from struct hmm_range

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 05:50:16PM +0000, Jason Gunthorpe wrote:
> The way ODP seems to work is once in hugetlb mode the dma addresses
> must give huge pages or the page fault will be failed. I think that is
> a terrible design, but this is how the driver is ..
> 
> So, from this HMM perspective if the caller asked for huge pages then
> the results have to be all huge pages or a hard failure.

Which isn't how the page_shift member works at moment.  It still
allows non-hugetlb mappings even with the member.

> It is not negotiated as an optimization like you are thinking.
> 
> [note, I haven't yet checked carefully how this works in ODP, every
>  time I look at parts of it the thing seems crazy]

This seems pretty crazy.  Especially as hugetlb use in applications
seems to fade in favour of THP, for which this ODP scheme does not seem
to work at all.

> > The best API for mlx4 would of course be to pass a biovec-style
> > variable length structure that hmm_fault could fill out, but that would
> > be a major restructure.
> 
> It would work, but the driver has to expand that into a page list
> right awayhow.
> 
> We can't even dma map the biovec with today's dma API as it needs the
> ability to remap on a page granularity.

We can do dma_map_page loops over each biovec entry pretty trivially,
and that won't be any worse than the current loop over each page in
the hmm dma helpers.  Once I get around the work to have a better
API for iommu mappings for bio_vecs we could coalesce it similar to
how we do it with scatterlist (but without all the mess of a new
structure).  That work is going to take a little longer through, as
it needs the amd and intell iommu drivers to be convered to dma-iommu
which isn't making progress as far as I hoped.

Let me know if you want to keep this code for now despite the issues,
or if we'd rather reimplement it once you've made sense of the ODP
code.

Re: [PATCH 11/13] mm: cleanup the hmm_vma_handle_pmd stub

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 05:53:14PM +0000, Jason Gunthorpe wrote:
> > -	/* If THP is not enabled then we should never reach this 
> 
> This old comment says we should never get here
> 
> > +}
> > +#else /* CONFIG_TRANSPARENT_HUGEPAGE */
> > +static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
> > +		unsigned long end, uint64_t *pfns, pmd_t pmd)
> > +{
> >  	return -EINVAL;
> 
> So could we just do
>    #define hmm_vma_handle_pmd NULL
> 
> ?
> 
> At the very least this seems like a WARN_ON too?

Despite the name of the function hmm_vma_handle_pmd is not a callback
for the pagewalk, but actually called from hmm_vma_handle_pmd.

What we could try is just and empty non-inline prototype without an
actual implementation, which means if the compiler doesn't optimize
the calls away we'll get a link error.

Re: [PATCH 13/13] mm: allow HMM_MIRROR on all architectures with MMU

[Christoph Hellwig]

On Tue, Jul 30, 2019 at 06:04:56PM +0000, Jason Gunthorpe wrote:
> Oh, can we make this into a non-user selectable option now? 
> 
> ie have the drivers that use the API select it?

Sure, I'll throw in another patch for that.