From 782f6bc0aba037436d6a04d19b23f8b61020a576 Mon Sep 17 00:00:00 2001 From: Akash Goel Date: Fri, 11 Mar 2016 14:56:42 +0530 Subject: [PATCH] drm/i915: Fixup the free space logic in ring_prepare Currently for the case where there is enough space at the end of Ring buffer for accommodating only the base request, the wrapround is done immediately and as a result the base request gets added at the start of Ring buffer. But there may not be enough free space at the beginning to accommodate the base request, as before the wraparound, the wait was effectively done for the reserved_size free space from the start of Ring buffer. In such a case there is a potential of Ring buffer overflow, the instructions at the head of Ring (ACTHD) can get overwritten. Since the base request can fit in the remaining space, there is no need to wraparound immediately. The wraparound will anyway happen later when the reserved part starts getting used. Cc: Chris Wilson Signed-off-by: Akash Goel Signed-off-by: Chris Wilson Link: http://patchwork.freedesktop.org/patch/msgid/1457688402-10411-1-git-send-email-akash.goel@intel.com Reviewed-by: Chris Wilson Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/intel_lrc.c | 6 +++--- drivers/gpu/drm/i915/intel_ringbuffer.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index a1db6a02cf23..67d48d759b46 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -854,11 +854,11 @@ static int logical_ring_prepare(struct drm_i915_gem_request *req, int bytes) if (unlikely(total_bytes > remain_usable)) { /* * The base request will fit but the reserved space - * falls off the end. So only need to to wait for the - * reserved size after flushing out the remainder. + * falls off the end. So don't need an immediate wrap + * and only need to effectively wait for the reserved + * size space from the start of ringbuffer. */ wait_bytes = remain_actual + ringbuf->reserved_size; - need_wrap = true; } else if (total_bytes > ringbuf->space) { /* No wrapping required, just waiting. */ wait_bytes = total_bytes; diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 6b4952031e30..39aa318ad779 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -2478,11 +2478,11 @@ static int __intel_ring_prepare(struct intel_engine_cs *engine, int bytes) if (unlikely(total_bytes > remain_usable)) { /* * The base request will fit but the reserved space - * falls off the end. So only need to to wait for the - * reserved size after flushing out the remainder. + * falls off the end. So don't need an immediate wrap + * and only need to effectively wait for the reserved + * size space from the start of ringbuffer. */ wait_bytes = remain_actual + ringbuf->reserved_size; - need_wrap = true; } else if (total_bytes > ringbuf->space) { /* No wrapping required, just waiting. */ wait_bytes = total_bytes; -- 2.20.1