drm/i915/selftests: exercise GPU access from the importer

Using PAGE_SIZE here potentially hides issues so bump that to something
larger. This should also make it possible for iommu to coalesce entries
for us. With that in place verify we can write from the GPU using the
importers sg_table, followed by checking that our writes match when read
from the CPU side.

v2: Switch over to igt_gpu_fill_dw(), which looks to be more widely
supported than the migrate stuff (at least OOTB).

References: https://gitlab.freedesktop.org/drm/intel/-/issues/7306Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221028155029.494736-2-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c

@@ -6,8 +6,12 @@
 
 #include "i915_drv.h"
 #include "i915_selftest.h"
+#include "gem/i915_gem_context.h"
 
+#include "mock_context.h"
 #include "mock_dmabuf.h"
+#include "igt_gem_utils.h"
+#include "selftests/mock_drm.h"
 #include "selftests/mock_gem_device.h"
 
 static int igt_dmabuf_export(void *arg)
@@ -140,6 +144,75 @@ static int igt_dmabuf_import_same_driver_lmem(void *arg)
 	return err;
 }
 
+static int verify_access(struct drm_i915_private *i915,
+			 struct drm_i915_gem_object *native_obj,
+			 struct drm_i915_gem_object *import_obj)
+{
+	struct i915_gem_engines_iter it;
+	struct i915_gem_context *ctx;
+	struct intel_context *ce;
+	struct i915_vma *vma;
+	struct file *file;
+	u32 *vaddr;
+	int err = 0, i;
+
+	file = mock_file(i915);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	ctx = live_context(i915, file);
+	if (IS_ERR(ctx)) {
+		err = PTR_ERR(ctx);
+		goto out_file;
+	}
+
+	for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
+		if (intel_engine_can_store_dword(ce->engine))
+			break;
+	}
+	i915_gem_context_unlock_engines(ctx);
+	if (!ce)
+		goto out_file;
+
+	vma = i915_vma_instance(import_obj, ce->vm, NULL);
+	if (IS_ERR(vma)) {
+		err = PTR_ERR(vma);
+		goto out_file;
+	}
+
+	err = i915_vma_pin(vma, 0, 0, PIN_USER);
+	if (err)
+		goto out_file;
+
+	err = igt_gpu_fill_dw(ce, vma, 0,
+			      vma->size >> PAGE_SHIFT, 0xdeadbeaf);
+	i915_vma_unpin(vma);
+	if (err)
+		goto out_file;
+
+	err = i915_gem_object_wait(import_obj, 0, MAX_SCHEDULE_TIMEOUT);
+	if (err)
+		goto out_file;
+
+	vaddr = i915_gem_object_pin_map_unlocked(native_obj, I915_MAP_WB);
+	if (IS_ERR(vaddr)) {
+		err = PTR_ERR(vaddr);
+		goto out_file;
+	}
+
+	for (i = 0; i < native_obj->base.size / sizeof(u32); i += PAGE_SIZE / sizeof(u32)) {
+		if (vaddr[i] != 0xdeadbeaf) {
+			pr_err("Data mismatch [%d]=%u\n", i, vaddr[i]);
+			err = -EINVAL;
+			goto out_file;
+		}
+	}
+
+out_file:
+	fput(file);
+	return err;
+}
+
 static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
 					 struct intel_memory_region **regions,
 					 unsigned int num_regions)
@@ -154,7 +227,7 @@ static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
 
 	force_different_devices = true;
 
-	obj = __i915_gem_object_create_user(i915, PAGE_SIZE,
+	obj = __i915_gem_object_create_user(i915, SZ_8M,
 					    regions, num_regions);
 	if (IS_ERR(obj)) {
 		pr_err("__i915_gem_object_create_user failed with err=%ld\n",
@@ -206,6 +279,10 @@ static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
 
 	i915_gem_object_unlock(import_obj);
 
+	err = verify_access(i915, obj, import_obj);
+	if (err)
+		goto out_import;
+
 	/* Now try a fake an importer */
 	import_attach = dma_buf_attach(dmabuf, obj->base.dev->dev);
 	if (IS_ERR(import_attach)) {