[PATCH v2 3/5] drm/i915: Add support for CPU mapping to DRM_IOCTL_I915_GEM_MMAP_GTT

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

This enables mapping via CPU using the proper DRM mmap API for
better debug (Valgrind) and implementation symmetry in the
driver.

v2:
 * Use normal mutex, skip domain management and pin pages. (Chris Wilson)
 * No need to drop struct mutex over vma_insert_pfn.
 * Turn off write-combine set up by the DRM core.
 * Commit message.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 98 ++++++++++++++++++++++++++++++++++++++---
 include/uapi/drm/i915_drm.h     |  3 ++
 2 files changed, 95 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a1e2832047e2..a690cee31f20 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1954,6 +1954,62 @@ out:
 	return i915_gem_ret_to_vm_ret(dev_priv, ret);
 }
 
+static int
+i915_gem_cpu_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct drm_i915_gem_object *obj = to_intel_bo(vma->vm_private_data);
+	struct drm_device *dev = obj->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool write = !!(vmf->flags & FAULT_FLAG_WRITE);
+	pgoff_t page_offset;
+	struct page *page;
+	unsigned long pgprot;
+	int ret;
+
+	/* We don't use vmf->pgoff since that has the fake offset */
+	page_offset = ((unsigned long)vmf->virtual_address - vma->vm_start) >>
+			PAGE_SHIFT;
+
+	trace_i915_gem_object_fault(obj, page_offset, true, write);
+
+	intel_runtime_pm_get(dev_priv);
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		goto out;
+
+	ret = i915_gem_object_get_pages(obj);
+	if (ret)
+		goto out_unlock;
+
+	i915_gem_object_pin_pages(obj);
+
+	page = i915_gem_object_get_page(obj, page_offset);
+	if (!page) {
+		ret = -EFAULT;
+		goto out_unpin;
+	}
+
+	ret = vm_insert_pfn(vma, (unsigned long)vmf->virtual_address,
+			    page_to_pfn(page));
+	if (ret == 0) {
+		/* DRM core sets up WC by default and we want WB. */
+		pgprot = pgprot_val(vm_get_page_prot(vma->vm_flags));
+		pgprot &= ~_PAGE_CACHE_MASK;
+		pgprot |= cachemode2protval(_PAGE_CACHE_MODE_WB);
+		vma->vm_page_prot = __pgprot(pgprot);
+	}
+
+out_unpin:
+	i915_gem_object_unpin_pages(obj);
+out_unlock:
+	mutex_unlock(&dev->struct_mutex);
+out:
+	intel_runtime_pm_put(dev_priv);
+
+	return i915_gem_ret_to_vm_ret(dev_priv, ret);
+}
+
 /**
  * i915_gem_release_mmap - remove physical page mappings
  * @obj: obj in question
@@ -2078,11 +2134,18 @@ static void i915_gem_object_free_mmap_offset(struct drm_i915_gem_object *obj)
 	drm_gem_free_mmap_offset(&obj->base);
 }
 
-int
-i915_gem_mmap_gtt(struct drm_file *file,
-		  struct drm_device *dev,
-		  uint32_t handle,
-		  uint64_t *offset)
+static const struct vm_operations_struct i915_gem_cpu_vm_ops = {
+	.fault = i915_gem_cpu_fault,
+	.open = drm_gem_vm_open,
+	.close = drm_gem_vm_close,
+};
+
+static int
+i915_gem_mmap(struct drm_file *file,
+	      struct drm_device *dev,
+	      uint32_t handle,
+	      uint32_t flags,
+	      uint64_t *offset)
 {
 	struct drm_i915_gem_object *obj;
 	int ret;
@@ -2103,10 +2166,23 @@ i915_gem_mmap_gtt(struct drm_file *file,
 		goto out;
 	}
 
+	if (!obj->base.filp && (flags & I915_MMAP2_CPU)) {
+		DRM_DEBUG("Attempting to mmap non-shm based object via CPU!\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
 	ret = i915_gem_object_create_mmap_offset(obj);
 	if (ret)
 		goto out;
 
+	if (flags & I915_MMAP2_CPU) {
+		ret = drm_vma_node_set_vm_ops(&obj->base.vma_node,
+					      &i915_gem_cpu_vm_ops);
+		if (ret)
+			goto out;
+	}
+
 	*offset = drm_vma_node_offset_addr(&obj->base.vma_node);
 
 out:
@@ -2116,6 +2192,15 @@ unlock:
 	return ret;
 }
 
+int
+i915_gem_mmap_gtt(struct drm_file *file,
+		  struct drm_device *dev,
+		  uint32_t handle,
+		  uint64_t *offset)
+{
+	return i915_gem_mmap(file, dev, handle, 0, offset);
+}
+
 /**
  * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
  * @dev: DRM device
@@ -2137,7 +2222,8 @@ i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_i915_gem_mmap_gtt *args = data;
 
-	return i915_gem_mmap_gtt(file, dev, args->handle, &args->offset);
+	return i915_gem_mmap(file, dev, args->handle, args->flags,
+			     &args->offset);
 }
 
 /* Immediately discard the backing storage */
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 6a19371391fa..359a36d604bb 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -528,6 +528,9 @@ struct drm_i915_gem_mmap_gtt {
 	 * This is a fixed-size type for 32/64 compatibility.
 	 */
 	__u64 offset;
+
+#define I915_MMAP2_CPU   0x1
+	__u64 flags;
 };
 
 struct drm_i915_gem_set_domain {
-- 
1.9.1

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