drm/i915/execlists: Use coherent writes into the context image

That we use a WB mapping for updating the RING_TAIL register inside the
context image even on !llc machines has been a source of consternation
for every reader. It appears to work on bsw+, but it may just have been
that we have been incredibly bad at detecting the errors.

v2: With extra enthusiasm.
v3: Drop force of map type for pinned default_state as by the time we
pin it, the map type is always WB and doesn't conflict with the earlier
use by ce->state.
v4: Transfer engine->default_state from MAP_WC to MAP_WB on creation so
we do not need the MAP_FORCE littered around the backends

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180914123504.2062-3-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ea6c6f7..0509fd0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3096,6 +3096,12 @@ enum i915_map_type {
        I915_MAP_FORCE_WC = I915_MAP_WC | I915_MAP_OVERRIDE,
 };
 
+static inline enum i915_map_type
+i915_coherent_map_type(struct drm_i915_private *i915)
+{
+       return HAS_LLC(i915) ? I915_MAP_WB : I915_MAP_WC;
+}
+
 /**
  * i915_gem_object_pin_map - return a contiguous mapping of the entire object
  * @obj: the object to map into kernel address space

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d276fb3..e3c2492 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5418,6 +5418,8 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
                struct i915_vma *state;
                void *vaddr;
 
+               GEM_BUG_ON(to_intel_context(ctx, engine)->pin_count);
+
                state = to_intel_context(ctx, engine)->state;
                if (!state)
                        continue;
@@ -5442,7 +5444,7 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
 
                /* Check we can acquire the image of the context state */
                vaddr = i915_gem_object_pin_map(engine->default_state,
-                                               I915_MAP_WB);
+                                               I915_MAP_FORCE_WB);
                if (IS_ERR(vaddr)) {
                        err = PTR_ERR(vaddr);
                        goto err_active;

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 3d7a052..664b96b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -1707,6 +1707,7 @@ static int gen8_configure_all_contexts(struct drm_i915_private *dev_priv,
                                       const struct i915_oa_config *oa_config)
 {
        struct intel_engine_cs *engine = dev_priv->engine[RCS];
+       unsigned int map_type = i915_coherent_map_type(dev_priv);
        struct i915_gem_context *ctx;
        struct i915_request *rq;
        int ret;
@@ -1741,7 +1742,7 @@ static int gen8_configure_all_contexts(struct drm_i915_private *dev_priv,
                if (!ce->state)
                        continue;
 
-               regs = i915_gem_object_pin_map(ce->state->obj, I915_MAP_WB);
+               regs = i915_gem_object_pin_map(ce->state->obj, map_type);
                if (IS_ERR(regs))
                        return PTR_ERR(regs);
 

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index d7fcbba..a51be16 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1294,7 +1294,7 @@ static int __context_pin(struct i915_gem_context *ctx, struct i915_vma *vma)
         * on an active context (which by nature is already on the GPU).
         */
        if (!(vma->flags & I915_VMA_GLOBAL_BIND)) {
-               err = i915_gem_object_set_to_gtt_domain(vma->obj, true);
+               err = i915_gem_object_set_to_wc_domain(vma->obj, true);
                if (err)
                        return err;
        }
@@ -1322,7 +1322,9 @@ __execlists_context_pin(struct intel_engine_cs *engine,
        if (ret)
                goto err;
 
-       vaddr = i915_gem_object_pin_map(ce->state->obj, I915_MAP_WB);
+       vaddr = i915_gem_object_pin_map(ce->state->obj,
+                                       i915_coherent_map_type(ctx->i915) |
+                                       I915_MAP_OVERRIDE);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                goto unpin_vma;