drm/i915: Record the default hw state after reset upon load

Take a copy of the HW state after a reset upon module loading by
executing a context switch from a blank context to the kernel context,
thus saving the default hw state over the blank context image.
We can then use the default hw state to initialise any future context,
ensuring that each starts with the default view of hw state.

v2: Unmap our default state from the GTT after stealing it from the
context. This should stop us from accidentally overwriting it via the
GTT (and frees up some precious GTT space).

Testcase: igt/gem_ctx_isolation
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110142634.10551-7-chris@chris-wilson.co.uk

1 files changed, 33 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 7e2a671882fb..464dc58af27b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1384,11 +1384,34 @@ alloc_context_vma(struct intel_engine_cs *engine)
         struct drm_i915_private *i915 = engine->i915;
         struct drm_i915_gem_object *obj;
         struct i915_vma *vma;
+        int err;
 
         obj = i915_gem_object_create(i915, engine->context_size);
         if (IS_ERR(obj))
                 return ERR_CAST(obj);
 
+        if (engine->default_state) {
+                void *defaults, *vaddr;
+
+                vaddr = i915_gem_object_pin_map(obj, I915_MAP_WB);
+                if (IS_ERR(vaddr)) {
+                        err = PTR_ERR(vaddr);
+                        goto err_obj;
+                }
+
+                defaults = i915_gem_object_pin_map(engine->default_state,
+                                                   I915_MAP_WB);
+                if (IS_ERR(defaults)) {
+                        err = PTR_ERR(defaults);
+                        goto err_map;
+                }
+
+                memcpy(vaddr, defaults, engine->context_size);
+
+                i915_gem_object_unpin_map(engine->default_state);
+                i915_gem_object_unpin_map(obj);
+        }
+
         /*
          * Try to make the context utilize L3 as well as LLC.
          *
@@ -1410,10 +1433,18 @@ alloc_context_vma(struct intel_engine_cs *engine)
         }
 
         vma = i915_vma_instance(obj, &i915->ggtt.base, NULL);
-        if (IS_ERR(vma))
-                i915_gem_object_put(obj);
+        if (IS_ERR(vma)) {
+                err = PTR_ERR(vma);
+                goto err_obj;
+        }
 
         return vma;
+
+err_map:
+        i915_gem_object_unpin_map(obj);
+err_obj:
+        i915_gem_object_put(obj);
+        return ERR_PTR(err);
 }
 
 static struct intel_ring *
@@ -1449,16 +1480,6 @@ intel_ring_context_pin(struct intel_engine_cs *engine,
                 ce->state->obj->pin_global++;
         }
 
-        /* The kernel context is only used as a placeholder for flushing the
-         * active context. It is never used for submitting user rendering and
-         * as such never requires the golden render context, and so we can skip
-         * emitting it when we switch to the kernel context. This is required
-         * as during eviction we cannot allocate and pin the renderstate in
-         * order to initialise the context.
-         */
-        if (i915_gem_context_is_kernel(ctx))
-                ce->initialised = true;
-
         i915_gem_context_get(ctx);
 
 out: