Commit dd68f2ba authored Mar 29, 2017 by Chris Wilson Committed by Jani Nikula Mar 29, 2017

drm/i915/execlists: Wrap tail pointer after reset tweaking



If the request->wa_tail is 0 (because it landed exactly on the end of
the ringbuffer), when we reconstruct request->tail following a reset we
fill in an illegal value (-8 or 0x001ffff8). As a result, RING_HEAD is
never able to catch up with RING_TAIL and the GPU spins endlessly. If
the ring contains a couple of breadcrumbs, even our hangcheck is unable
to catch the busy-looping as the ACTHD and seqno continually advance.

v2: Move the wrap into a common intel_ring_wrap().

Fixes: a3aabe86 ("drm/i915/execlists: Reinitialise context image after GPU hang")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: <stable@vger.kernel.org> # v4.10+
Link: http://patchwork.freedesktop.org/patch/msgid/20170327130009.4678-1-chris@chris-wilson.co.uk


Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
(cherry picked from commit 450362d3)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170329121315.1290-1-chris@chris-wilson.co.uk

parent aa62acfd

drivers/gpu/drm/i915/intel_lrc.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -1440,7 +1440,9 @@ static void reset_common_ring(struct intel_engine_cs *engine,
		GEM_BUG_ON(request->ctx != port[0].request->ctx);

		/* Reset WaIdleLiteRestore:bdw,skl as well */
		request->tail = request->wa_tail - WA_TAIL_DWORDS * sizeof(u32);
		request->tail =
		intel_ring_wrap(request->ring,
		request->wa_tail - WA_TAIL_DWORDS*sizeof(u32));
		}

		static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)

drivers/gpu/drm/i915/intel_ringbuffer.h

+7 −1

Original line number	Diff line number	Diff line
		@@ -521,11 +521,17 @@ static inline void intel_ring_advance(struct intel_ring *ring)
		*/
		}

		static inline u32
		intel_ring_wrap(const struct intel_ring *ring, u32 pos)
		{
		return pos & (ring->size - 1);
		}

		static inline u32 intel_ring_offset(struct intel_ring ring, void addr)
		{
		/* Don't write ring->size (equivalent to 0) as that hangs some GPUs. */
		u32 offset = addr - ring->vaddr;
		return offset & (ring->size - 1);
		return intel_ring_wrap(ring, offset);
		}

		int __intel_ring_space(int head, int tail, int size);