3.19-stable review patch. If anyone has any objections, please let me know.
------------------ From: Chris Wilson <[email protected]> commit f0a1fb10e5f79f5aaf8d7e94b9fa6bf2fa9aeebf upstream. This looked like an odd regression from commit ec5cc0f9b019af95e4571a9fa162d94294c8d90b Author: Chris Wilson <[email protected]> Date: Thu Jun 12 10:28:55 2014 +0100 drm/i915: Restrict GPU boost to the RCS engine but in reality it undercovered a much older coherency bug. The issue that boosting the GPU frequency on the BCS ring was masking was that we could wake the CPU up after completion of a BCS batch and inspect memory prior to the write cache being fully evicted. In order to serialise the breadcrumb interrupt (and so ensure that the CPU's view of memory is coherent) we need to perform a post-sync operation in the MI_FLUSH_DW. v2: Fix all the MI_FLUSH_DW (bsd plus the duplication in execlists). Also fix the invalidate_domains mask in gen8_emit_flush() for ring != VCS. Testcase: gpuX-rcs-gpu-read-after-write Signed-off-by: Chris Wilson <[email protected]> Acked-by: Daniel Vetter <[email protected]> Signed-off-by: Jani Nikula <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/gpu/drm/i915/intel_lrc.c | 20 +++++++++++--------- drivers/gpu/drm/i915/intel_ringbuffer.c | 23 +++++++++++++++++++---- 2 files changed, 30 insertions(+), 13 deletions(-) --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -1237,15 +1237,17 @@ static int gen8_emit_flush(struct intel_ cmd = MI_FLUSH_DW + 1; - if (ring == &dev_priv->ring[VCS]) { - if (invalidate_domains & I915_GEM_GPU_DOMAINS) - cmd |= MI_INVALIDATE_TLB | MI_INVALIDATE_BSD | - MI_FLUSH_DW_STORE_INDEX | - MI_FLUSH_DW_OP_STOREDW; - } else { - if (invalidate_domains & I915_GEM_DOMAIN_RENDER) - cmd |= MI_INVALIDATE_TLB | MI_FLUSH_DW_STORE_INDEX | - MI_FLUSH_DW_OP_STOREDW; + /* We always require a command barrier so that subsequent + * commands, such as breadcrumb interrupts, are strictly ordered + * wrt the contents of the write cache being flushed to memory + * (and thus being coherent from the CPU). + */ + cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW; + + if (invalidate_domains & I915_GEM_GPU_DOMAINS) { + cmd |= MI_INVALIDATE_TLB; + if (ring == &dev_priv->ring[VCS]) + cmd |= MI_INVALIDATE_BSD; } intel_logical_ring_emit(ringbuf, cmd); --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -2178,6 +2178,14 @@ static int gen6_bsd_ring_flush(struct in cmd = MI_FLUSH_DW; if (INTEL_INFO(ring->dev)->gen >= 8) cmd += 1; + + /* We always require a command barrier so that subsequent + * commands, such as breadcrumb interrupts, are strictly ordered + * wrt the contents of the write cache being flushed to memory + * (and thus being coherent from the CPU). + */ + cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW; + /* * Bspec vol 1c.5 - video engine command streamer: * "If ENABLED, all TLBs will be invalidated once the flush @@ -2185,8 +2193,8 @@ static int gen6_bsd_ring_flush(struct in * Post-Sync Operation field is a value of 1h or 3h." */ if (invalidate & I915_GEM_GPU_DOMAINS) - cmd |= MI_INVALIDATE_TLB | MI_INVALIDATE_BSD | - MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW; + cmd |= MI_INVALIDATE_TLB | MI_INVALIDATE_BSD; + intel_ring_emit(ring, cmd); intel_ring_emit(ring, I915_GEM_HWS_SCRATCH_ADDR | MI_FLUSH_DW_USE_GTT); if (INTEL_INFO(ring->dev)->gen >= 8) { @@ -2282,6 +2290,14 @@ static int gen6_ring_flush(struct intel_ cmd = MI_FLUSH_DW; if (INTEL_INFO(ring->dev)->gen >= 8) cmd += 1; + + /* We always require a command barrier so that subsequent + * commands, such as breadcrumb interrupts, are strictly ordered + * wrt the contents of the write cache being flushed to memory + * (and thus being coherent from the CPU). + */ + cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW; + /* * Bspec vol 1c.3 - blitter engine command streamer: * "If ENABLED, all TLBs will be invalidated once the flush @@ -2289,8 +2305,7 @@ static int gen6_ring_flush(struct intel_ * Post-Sync Operation field is a value of 1h or 3h." */ if (invalidate & I915_GEM_DOMAIN_RENDER) - cmd |= MI_INVALIDATE_TLB | MI_FLUSH_DW_STORE_INDEX | - MI_FLUSH_DW_OP_STOREDW; + cmd |= MI_INVALIDATE_TLB; intel_ring_emit(ring, cmd); intel_ring_emit(ring, I915_GEM_HWS_SCRATCH_ADDR | MI_FLUSH_DW_USE_GTT); if (INTEL_INFO(ring->dev)->gen >= 8) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
