Currently we just leave it uninitialised, which at first looks harmless,
however we also don't zero out the pfn array, and with pfn_flags_mask
the idea is to be able set individual flags for a given range of pfn or
completely ignore them, outside of default_flags. So here we end up with
pfn[i] & pfn_flags_mask, and if both are uninitialised we might get back
an unexpected flags value, like asking for read only with default_flags,
but getting back write on top, leading to potentially bogus behaviour.
To fix this ensure we zero the pfn_flags_mask, such that hmm only
considers the default_flags and not also the initial pfn[i] value.
v2 (Thomas):
- Prefer proper initializer.
Fixes: 81e058a3e7fd ("drm/xe: Introduce helper to populate userptr")
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.10+
---
drivers/gpu/drm/xe/xe_hmm.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_hmm.c b/drivers/gpu/drm/xe/xe_hmm.c
index 089834467880..2e4ae61567d8 100644
--- a/drivers/gpu/drm/xe/xe_hmm.c
+++ b/drivers/gpu/drm/xe/xe_hmm.c
@@ -166,13 +166,20 @@ int xe_hmm_userptr_populate_range(struct xe_userptr_vma *uvma,
{
unsigned long timeout =
jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
- unsigned long *pfns, flags = HMM_PFN_REQ_FAULT;
+ unsigned long *pfns;
struct xe_userptr *userptr;
struct xe_vma *vma = &uvma->vma;
u64 userptr_start = xe_vma_userptr(vma);
u64 userptr_end = userptr_start + xe_vma_size(vma);
struct xe_vm *vm = xe_vma_vm(vma);
- struct hmm_range hmm_range;
+ struct hmm_range hmm_range = {
+ .pfn_flags_mask = 0, /* ignore pfns */
+ .default_flags = HMM_PFN_REQ_FAULT,
+ .start = userptr_start,
+ .end = userptr_end,
+ .notifier = &uvma->userptr.notifier,
+ .dev_private_owner = vm->xe,
+ };
bool write = !xe_vma_read_only(vma);
unsigned long notifier_seq;
u64 npages;
@@ -199,19 +206,14 @@ int xe_hmm_userptr_populate_range(struct xe_userptr_vma *uvma,
return -ENOMEM;
if (write)
- flags |= HMM_PFN_REQ_WRITE;
+ hmm_range.default_flags |= HMM_PFN_REQ_WRITE;
if (!mmget_not_zero(userptr->notifier.mm)) {
ret = -EFAULT;
goto free_pfns;
}
- hmm_range.default_flags = flags;
hmm_range.hmm_pfns = pfns;
- hmm_range.notifier = &userptr->notifier;
- hmm_range.start = userptr_start;
- hmm_range.end = userptr_end;
- hmm_range.dev_private_owner = vm->xe;
while (true) {
hmm_range.notifier_seq = mmu_interval_read_begin(&userptr->notifier);
--
2.48.1
