From d323c9b88260bc2cf3e3ed4bc741ab69643e0233 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 11 Nov 2019 13:32:04 +0000 Subject: [PATCH] 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: 5b56d49fc31d ("mm: add locked parameter to get_user_pages_remote()") Testcase: igt/gem_userptr/userfault Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20191111133205.11590-2-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c index dd104b0e2071..54ebc7ab71bc 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c @@ -459,26 +459,31 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work) if (pvec != NULL) { struct mm_struct *mm = obj->userptr.mm->mm; unsigned int flags = 0; + int locked = 0; if (!i915_gem_object_is_readonly(obj)) flags |= FOLL_WRITE; ret = -EFAULT; if (mmget_not_zero(mm)) { - down_read(&mm->mmap_sem); while (pinned < npages) { + if (!locked) { + down_read(&mm->mmap_sem); + locked = 1; + } ret = get_user_pages_remote (work->task, mm, obj->userptr.ptr + pinned * PAGE_SIZE, npages - pinned, flags, - pvec + pinned, NULL, NULL); + pvec + pinned, NULL, &locked); if (ret < 0) break; pinned += ret; } - up_read(&mm->mmap_sem); + if (locked) + up_read(&mm->mmap_sem); mmput(mm); } } -- GitLab