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Subject[PATCH 08/14] mm/hmm: cleanup special vma handling (VM_SPECIAL)
Date
From: Jérôme Glisse <jglisse@redhat.com>

Special vma (one with any of the VM_SPECIAL flags) can not be access by
device because there is no consistent model accross device drivers on
those vma and their backing memory.

This patch directly use hmm_range struct for hmm_pfns_special() argument
as it is always affecting the whole vma and thus the whole range.

It also make behavior consistent after this patch both hmm_vma_fault()
and hmm_vma_get_pfns() returns -EINVAL when facing such vma. Previously
hmm_vma_fault() returned 0 and hmm_vma_get_pfns() return -EINVAL but
both were filling the HMM pfn array with special entry.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
---
mm/hmm.c | 40 ++++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index f674b73e7f4a..04595a994542 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -281,14 +281,6 @@ static int hmm_vma_do_fault(struct mm_walk *walk,
return -EAGAIN;
}

-static void hmm_pfns_special(uint64_t *pfns,
- unsigned long addr,
- unsigned long end)
-{
- for (; addr < end; addr += PAGE_SIZE, pfns++)
- *pfns = HMM_PFN_SPECIAL;
-}
-
static int hmm_pfns_bad(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
@@ -486,6 +478,14 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
return 0;
}

+static void hmm_pfns_special(struct hmm_range *range)
+{
+ unsigned long addr = range->start, i = 0;
+
+ for (; addr < range->end; addr += PAGE_SIZE, i++)
+ range->pfns[i] = HMM_PFN_SPECIAL;
+}
+
/*
* hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
* @range: range being snapshoted and all needed informations
@@ -509,12 +509,6 @@ int hmm_vma_get_pfns(struct hmm_range *range)
struct mm_walk mm_walk;
struct hmm *hmm;

- /* FIXME support hugetlb fs */
- if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
- hmm_pfns_special(range->pfns, range->start, range->end);
- return -EINVAL;
- }
-
/* Sanity check, this really should not happen ! */
if (range->start < vma->vm_start || range->start >= vma->vm_end)
return -EINVAL;
@@ -528,6 +522,12 @@ int hmm_vma_get_pfns(struct hmm_range *range)
if (!hmm->mmu_notifier.ops)
return -EINVAL;

+ /* FIXME support hugetlb fs */
+ if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+ hmm_pfns_special(range);
+ return -EINVAL;
+ }
+
/* Initialize range to track CPU page table update */
spin_lock(&hmm->lock);
range->valid = true;
@@ -693,6 +693,12 @@ int hmm_vma_fault(struct hmm_range *range, bool write, bool block)
if (!hmm->mmu_notifier.ops)
return -EINVAL;

+ /* FIXME support hugetlb fs */
+ if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+ hmm_pfns_special(range);
+ return -EINVAL;
+ }
+
/* Initialize range to track CPU page table update */
spin_lock(&hmm->lock);
range->valid = true;
@@ -710,12 +716,6 @@ int hmm_vma_fault(struct hmm_range *range, bool write, bool block)
return 0;
}

- /* FIXME support hugetlb fs */
- if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
- hmm_pfns_special(range->pfns, range->start, range->end);
- return 0;
- }
-
hmm_vma_walk.fault = true;
hmm_vma_walk.write = write;
hmm_vma_walk.block = block;
--
2.14.3
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