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Commit 349f2ccf authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Move the mb() following release-mmap into release-mmap 



As paranoia, we want to ensure that the CPU's PTEs have been revoked for
the object before we return from i915_gem_release_mmap(). This allows us
to rely on there being no outstanding memory accesses from userspace
and guarantees serialisation of the code against concurrent access just
by calling i915_gem_release_mmap().

v2: Reduce the mb() into a wmb() following the revoke.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: "Goel, Akash" <akash.goel@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1460565315-7748-13-git-send-email-chris@chris-wilson.co.uk
parent a687a43a

drivers/gpu/drm/i915/i915_gem.c

+16 −3
Original line number Original line Diff line number Diff line
@@ -1936,11 +1936,27 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
void

void

i915_gem_release_mmap(struct drm_i915_gem_object *obj)

i915_gem_release_mmap(struct drm_i915_gem_object *obj)

{

{

	/* Serialisation between user GTT access and our code depends upon

	 * revoking the CPU's PTE whilst the mutex is held. The next user

	 * pagefault then has to wait until we release the mutex.

	 */

	lockdep_assert_held(&obj->base.dev->struct_mutex);



	if (!obj->fault_mappable)

	if (!obj->fault_mappable)

		return;

		return;





	drm_vma_node_unmap(&obj->base.vma_node,

	drm_vma_node_unmap(&obj->base.vma_node,

			   obj->base.dev->anon_inode->i_mapping);

			   obj->base.dev->anon_inode->i_mapping);



	/* Ensure that the CPU's PTE are revoked and there are not outstanding

	 * memory transactions from userspace before we return. The TLB

	 * flushing implied above by changing the PTE above *should* be

	 * sufficient, an extra barrier here just provides us with a bit

	 * of paranoid documentation about our requirement to serialise

	 * memory writes before touching registers / GSM.

	 */

	wmb();



	obj->fault_mappable = false;

	obj->fault_mappable = false;

}

}
@@ -3324,9 +3340,6 @@ static void i915_gem_object_finish_gtt(struct drm_i915_gem_object *obj) 
	if ((obj->base.read_domains & I915_GEM_DOMAIN_GTT) == 0)

	if ((obj->base.read_domains & I915_GEM_DOMAIN_GTT) == 0)

		return;

		return;





	/* Wait for any direct GTT access to complete */

	mb();



	old_read_domains = obj->base.read_domains;

	old_read_domains = obj->base.read_domains;

	old_write_domain = obj->base.write_domain;

	old_write_domain = obj->base.write_domain;