Hi Greg&stable-team, The below patch papers over a graphics corruption issue in 3.5/3.6. The regression happened due to pwrite tunings in 3.5, which made cpu relocations much more likely. The issue seems to have disappeared in 3.7-rc1, but it takes a few days to test a patch, so we haven't figured out what exactly fixed things. Now users are taking out their pitchforks already, so instead of wasting more days (maybe weeks?) to fully understand the bug before backporting the fix, we've opted for the below disable patch, which should have minimal impact (at most it undoes the tuning improvements in 3.5). Patch is tested by reporters & acked by all relevant ppl, please apply to 3.5/3.6 series kernels. Thanks, Daniel --- They seem to be implicated in render corruptions. And up to now no one really seems to understand the issue, so let's just disable them for now. Most of the machines exhibiting this issue have only a 128 gtt mmio window, so increased pressure on the mappable part (and so higher chance for cpu relocs) seems to be the key. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=852210 Tested-by: Dave Airlie <airlied at gmail.com> Cc: stable at vger.kernel.org Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org> Acked-by: Chris Wilson <chris at chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> --- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index ff2819e..682156a 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -268,6 +268,12 @@ eb_destroy(struct eb_objects *eb) static inline int use_cpu_reloc(struct drm_i915_gem_object *obj) { + /* cpu relocs are implicated in some not-yet-understood render + * corruptions on at least ilk, but probably also gm45. Until we know + * what's going on, just disable them. */ + if (INTEL_INFO(obj->base.dev)->gen < 6) + return false; + return (obj->base.write_domain == I915_GEM_DOMAIN_CPU || obj->cache_level != I915_CACHE_NONE); } -- 1.7.10.4
