[Intel-gfx] [PATCH] drm/i915/guc: Delay GuC workqueue reservation

[Michał Winiarski]

We're reserving space in the workqueue early during request allocation.
This can be problematic if we get interrupted later in the process,
because we can end up in a state where GuC workqueue is seemingly full,
while the HW is idle and no work has been submitted.
Let's delay the reservation to avoid such scenario.

Testcase: igt/gem_ringfill/*-interruptible
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97978
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Jeff Mcgee <jeff.mcgee at intel.com>
Signed-off-by: Michał Winiarski <michal.winiarski at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 11 +++++++++++
 drivers/gpu/drm/i915/intel_lrc.c           | 11 -----------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index e88786e..37204db 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1529,6 +1529,17 @@ execbuf_submit(struct i915_execbuffer_params *params,
 	if (ret)
 		return ret;
 
+	if (i915.enable_guc_submission) {
+		/*
+		 * Check that the GuC has space for the request before
+		 * going any further, as the i915_add_request() call
+		 * later on mustn't fail ...
+		 */
+		ret = i915_guc_wq_reserve(params->request);
+		if (ret)
+			return ret;
+	}
+
 	trace_i915_gem_ring_dispatch(params->request, params->dispatch_flags);
 
 	i915_gem_execbuffer_move_to_active(vmas, params->request);
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 936f6f6..cc8fd03 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -626,17 +626,6 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
 
 	request->ring = ce->ring;
 
-	if (i915.enable_guc_submission) {
-		/*
-		 * Check that the GuC has space for the request before
-		 * going any further, as the i915_add_request() call
-		 * later on mustn't fail ...
-		 */
-		ret = i915_guc_wq_reserve(request);
-		if (ret)
-			return ret;
-	}
-
 	ret = intel_lr_context_pin(request->ctx, engine);
 	if (ret)
 		return ret;
-- 
2.7.4