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mm/hmm: allow hmm_range to be used with a mmu_interval_notifier or hmm_mirror 

hmm_mirror's handling of ranges does not use a sequence count which
results in this bug:

         CPU0                                   CPU1
                                     hmm_range_wait_until_valid(range)
                                         valid == true
                                     hmm_range_fault(range)
hmm_invalidate_range_start()
   range->valid = false
hmm_invalidate_range_end()
   range->valid = true
                                     hmm_range_valid(range)
                                          valid == true

Where the hmm_range_valid() should not have succeeded.

Adding the required sequence count would make it nearly identical to the
new mmu_interval_notifier. Instead replace the hmm_mirror stuff with
mmu_interval_notifier.

Co-existence of the two APIs is the first step.

Link: https://lore.kernel.org/r/20191112202231.3856-4-jgg@ziepe.ca
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Tested-by: Philip Yang <Philip.Yang@amd.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2019-11-12 16:22:20 -04:00
parent 99cb252f5e
commit 04ec32fbc2
2 changed files with 24 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/hmm.h
View File

@ -145,6 +145,9 @@ enum hmm_pfn_value_e {
/*
* struct hmm_range - track invalidation lock on virtual address range
*
* @notifier: an optional mmu_interval_notifier
* @notifier_seq: when notifier is used this is the result of
* mmu_interval_read_begin()
* @hmm: the core HMM structure this range is active against
* @vma: the vm area struct for the range
* @list: all range lock are on a list
@ -159,6 +162,8 @@ enum hmm_pfn_value_e {
* @valid: pfns array did not change since it has been fill by an HMM function
*/
struct hmm_range {
struct mmu_interval_notifier *notifier;
unsigned long notifier_seq;
struct hmm *hmm;
struct list_head list;
unsigned long start;

25
mm/hmm.c
View File

@ -858,6 +858,14 @@ void hmm_range_unregister(struct hmm_range *range)
}
EXPORT_SYMBOL(hmm_range_unregister);
static bool needs_retry(struct hmm_range *range)
{
if (range->notifier)
return mmu_interval_check_retry(range->notifier,
range->notifier_seq);
return !range->valid;
}
static const struct mm_walk_ops hmm_walk_ops = {
.pud_entry = hmm_vma_walk_pud,
.pmd_entry = hmm_vma_walk_pmd,
@ -898,18 +906,23 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
unsigned long start = range->start, end;
struct hmm_vma_walk hmm_vma_walk;
struct hmm *hmm = range->hmm;
struct mm_struct *mm;
struct vm_area_struct *vma;
int ret;
lockdep_assert_held(&hmm->mmu_notifier.mm->mmap_sem);
if (range->notifier)
mm = range->notifier->mm;
else
mm = range->hmm->mmu_notifier.mm;
lockdep_assert_held(&mm->mmap_sem);
do {
/* If range is no longer valid force retry. */
if (!range->valid)
if (needs_retry(range))
return -EBUSY;
vma = find_vma(hmm->mmu_notifier.mm, start);
vma = find_vma(mm, start);
if (vma == NULL || (vma->vm_flags & device_vma))
return -EFAULT;
@ -939,7 +952,7 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
start = hmm_vma_walk.last;
/* Keep trying while the range is valid. */
} while (ret == -EBUSY && range->valid);
} while (ret == -EBUSY && !needs_retry(range));
if (ret) {
unsigned long i;
@ -997,7 +1010,7 @@ long hmm_range_dma_map(struct hmm_range *range, struct device *device,
continue;
/* Check if range is being invalidated */
if (!range->valid) {
if (needs_retry(range)) {
ret = -EBUSY;
goto unmap;
}