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drm/i915/userptr: Handle unlocked gup retries 

Enable gup to retry and fault the pages outside of the mmap_sem lock in
our worker. As we are inside our worker, outside of any critical path,
we can allow the mmap_sem lock to be dropped in order to service a page
fault; this in turn allows the mm to populate the page using a slow
fault handler.

References: 5b56d49fc3 ("mm: add locked parameter to get_user_pages_remote()")
Testcase: igt/gem_userptr/userfault
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191111133205.11590-2-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2019-11-11 13:32:04 +00:00
parent 0d4bbe3d40
commit d323c9b882
1 changed files with 8 additions and 3 deletions
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11
drivers/gpu/drm/i915/gem/i915_gem_userptr.c
View File

@ -459,26 +459,31 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
if (pvec != NULL) { if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm->mm; struct mm_struct *mm = obj->userptr.mm->mm;
unsigned int flags = 0; unsigned int flags = 0;
int locked = 0;
if (!i915_gem_object_is_readonly(obj)) if (!i915_gem_object_is_readonly(obj))
flags |= FOLL_WRITE; flags |= FOLL_WRITE;
ret = -EFAULT; ret = -EFAULT;
if (mmget_not_zero(mm)) { if (mmget_not_zero(mm)) {
down_read(&mm->mmap_sem);
while (pinned < npages) { while (pinned < npages) {
if (!locked) {
down_read(&mm->mmap_sem);
locked = 1;
}
ret = get_user_pages_remote ret = get_user_pages_remote
(work->task, mm, (work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE, obj->userptr.ptr + pinned * PAGE_SIZE,
npages - pinned, npages - pinned,
flags, flags,
pvec + pinned, NULL, NULL); pvec + pinned, NULL, &locked);
if (ret < 0) if (ret < 0)
break; break;
pinned += ret; pinned += ret;
} }
up_read(&mm->mmap_sem); if (locked)
up_read(&mm->mmap_sem);
mmput(mm); mmput(mm);
} }
} }