From d70af57944a1593f2cd6f94b7eb29fae97929953 Mon Sep 17 00:00:00 2001 From: Matthew Auld Date: Mon, 18 Oct 2021 18:45:05 +0100 Subject: [PATCH] drm/i915/shmem: ensure flush during swap-in on non-LLC MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On non-LLC platforms, force the flush-on-acquire if this is ever swapped-in. Our async flush path is not trust worthy enough yet(and happens in the wrong order), and with some tricks it's conceivable for userspace to change the cache-level to I915_CACHE_NONE after the pages are swapped-in, and since execbuf binds the object before doing the async flush, there is a potential race window. Signed-off-by: Matthew Auld Cc: Thomas Hellström Reviewed-by: Thomas Hellström Link: https://patchwork.freedesktop.org/patch/msgid/20211018174508.2137279-6-matthew.auld@intel.com --- drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c index cf11aa7..d77da59 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c @@ -286,6 +286,8 @@ __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj, struct sg_table *pages, bool needs_clflush) { + struct drm_i915_private *i915 = to_i915(obj->base.dev); + GEM_BUG_ON(obj->mm.madv == __I915_MADV_PURGED); if (obj->mm.madv == I915_MADV_DONTNEED) @@ -297,6 +299,16 @@ __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj, drm_clflush_sg(pages); __start_cpu_write(obj); + /* + * On non-LLC platforms, force the flush-on-acquire if this is ever + * swapped-in. Our async flush path is not trust worthy enough yet(and + * happens in the wrong order), and with some tricks it's conceivable + * for userspace to change the cache-level to I915_CACHE_NONE after the + * pages are swapped-in, and since execbuf binds the object before doing + * the async flush, we have a race window. + */ + if (!HAS_LLC(i915)) + obj->cache_dirty = true; } void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_table *pages) -- 2.7.4