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Commit 855ce7d2 authored by Jérôme Glisse's avatar Jérôme Glisse Committed by Linus Torvalds
Browse files

mm/hmm: cleanup special vma handling (VM_SPECIAL) 

Special vma (one with any of the VM_SPECIAL flags) can not be access by
device because there is no consistent model across 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.

Link: http://lkml.kernel.org/r/20180323005527.758-10-jglisse@redhat.com


Signed-off-by: default avatarJérôme Glisse <jglisse@redhat.com>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ff05c0c6

mm/hmm.c

+20 −20
Original line number Diff line number Diff line
@@ -324,14 +324,6 @@ 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)
@@ -529,6 +521,14 @@ 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 snapshotted
@@ -553,12 +553,6 @@ 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;
@@ -572,6 +566,12 @@ 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;

	}



	if (!(vma->vm_flags & VM_READ)) {

		/*

		 * If vma do not allow read access, then assume that it does
@@ -740,6 +740,12 @@ 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;

	}



	if (!(vma->vm_flags & VM_READ)) {

		/*

		 * If vma do not allow read access, then assume that it does
@@ -751,12 +757,6 @@ int hmm_vma_fault(struct hmm_range *range, bool write, bool block) 
		return -EPERM;

	}



	/* 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;

	}



	/* Initialize range to track CPU page table update */

	spin_lock(&hmm->lock);

	range->valid = true;