drm/i915/gt: Keep a no-frills swappable copy of the default context state

We need to keep the default context state around to instantiate new
contexts (aka golden rendercontext), and we also keep it pinned while
the engine is active so that we can quickly reset a hanging context.
However, the default contexts are large enough to merit keeping in
swappable memory as opposed to kernel memory, so we store them inside
shmemfs. Currently, we use the normal GEM objects to create the default
context image, but we can throw away all but the shmemfs file.

This greatly simplifies the tricky power management code which wants to
run underneath the normal GT locking, and we definitely do not want to
use any high level objects that may appear to recurse back into the GT.
Though perhaps the primary advantage of the complex GEM object is that
we aggressively cache the mapping, but here we are recreating the
vm_area everytime time we unpark. At the worst, we add a lightweight
cache, but first find a microbenchmark that is impacted.

Having started to create some utility functions to make working with
shmemfs objects easier, we can start putting them to wider use, where
GEM objects are overkill, such as storing persistent error state.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200429172429.6054-1-chris@chris-wilson.co.uk

1 files changed, 0 insertions, 26 deletions

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index a976cd67b3b3..eec292d06f11 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1320,26 +1320,6 @@ capture_user(struct intel_engine_capture_vma *capture,
 	return capture;
 }
 
-static struct i915_vma_coredump *
-capture_object(const struct intel_gt *gt,
-	       struct drm_i915_gem_object *obj,
-	       const char *name,
-	       struct i915_vma_compress *compress)
-{
-	if (obj && i915_gem_object_has_pages(obj)) {
-		struct i915_vma fake = {
-			.node = { .start = U64_MAX, .size = obj->base.size },
-			.size = obj->base.size,
-			.pages = obj->mm.pages,
-			.obj = obj,
-		};
-
-		return i915_vma_coredump_create(gt, &fake, name, compress);
-	} else {
-		return NULL;
-	}
-}
-
 static void add_vma(struct intel_engine_coredump *ee,
 		    struct i915_vma_coredump *vma)
 {
@@ -1428,12 +1408,6 @@ intel_engine_coredump_add_vma(struct intel_engine_coredump *ee,
 					 engine->wa_ctx.vma,
 					 "WA context",
 					 compress));
-
-	add_vma(ee,
-		capture_object(engine->gt,
-			       engine->default_state,
-			       "NULL context",
-			       compress));
 }
 
 static struct intel_engine_coredump *