[Intel-gfx] [PATCH 3/5] drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET

[Abdiel Janulgue]

This is really just an alias of mmap_gtt. The 'mmap offset' nomenclature
comes from the value returned by this ioctl which is the offset into the
device fd which userpace uses with mmap(2).

mmap_gtt was our initial mmap_offset implementation, this extends
our CPU mmap support to allow additional fault handlers that depends on
the object's backing pages.

Note that we multiplex mmap_gtt and mmap_offset through the same ioctl,
and use the zero extending behaviour of drm to differentiate between
them, when we inspect the flags.

v2:
- Drop the alias, just rename the struct (Chris)
- Don't bail out on no PAT when doing WB mmaps
- Prepare uAPI for further extensions
v3:
- drop MMAP_OFFSET_FLAGS

Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c      | 44 ++++++++++++++++++-
 .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 ++
 include/uapi/drm/i915_drm.h                   | 27 +++++++++++-
 3 files changed, 71 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 3491bb06606b..a3eb194fd3b4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -144,6 +144,9 @@ static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)
  * 3 - Remove implicit set-domain(GTT) and synchronisation on initial
  *     pagefault; swapin remains transparent.
  *
+ * 4 - Support multiple fault handlers per object depending on object's
+ *     backing storage (a.k.a. MMAP_OFFSET).
+ *
  * Restrictions:
  *
  *  * snoopable objects cannot be accessed via the GTT. It can cause machine
@@ -171,7 +174,7 @@ static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)
  */
 int i915_gem_mmap_gtt_version(void)
 {
-	return 3;
+	return 4;
 }
 
 static inline struct i915_ggtt_view
@@ -534,6 +537,35 @@ __assign_gem_object_mmap_data(struct drm_file *file,
 	return ret;
 }
 
+static int gem_mmap_offset(struct drm_device *dev, void *data,
+			   struct drm_file *file)
+{
+	struct drm_i915_gem_mmap_offset *args = data;
+	enum i915_mmap_type type;
+
+	switch (args->flags) {
+	case I915_MMAP_OFFSET_WC:
+		if (!boot_cpu_has(X86_FEATURE_PAT))
+			return -ENODEV;
+		type = I915_MMAP_TYPE_WC;
+		break;
+	case I915_MMAP_OFFSET_WB:
+		type = I915_MMAP_TYPE_WB;
+		break;
+	case I915_MMAP_OFFSET_UC:
+		if (!boot_cpu_has(X86_FEATURE_PAT))
+			return -ENODEV;
+		type = I915_MMAP_TYPE_UC;
+		break;
+	default:
+		return -EINVAL;
+
+	};
+
+	return __assign_gem_object_mmap_data(file, args->handle, type,
+					     &args->offset);
+}
+
 /**
  * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
  * @dev: DRM device
@@ -553,7 +585,15 @@ int
 i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
 			struct drm_file *file)
 {
-	struct drm_i915_gem_mmap_gtt *args = data;
+	struct drm_i915_gem_mmap_offset *args = data;
+	struct drm_i915_private *i915 = to_i915(dev);
+
+	if (args->flags)
+		return gem_mmap_offset(dev, data, file);
+
+	if (!HAS_MAPPABLE_APERTURE(i915))
+		/* No aperture, cannot mmap via legacy GTT */
+		return -ENODEV;
 
 	return __assign_gem_object_mmap_data(file, args->handle,
 					     I915_MMAP_TYPE_GTT,
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index c5c305bd9927..c643d45f5c0d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -64,6 +64,9 @@ struct drm_i915_gem_object_ops {
 
 enum i915_mmap_type {
 	I915_MMAP_TYPE_GTT = 0,
+	I915_MMAP_TYPE_WC,
+	I915_MMAP_TYPE_WB,
+	I915_MMAP_TYPE_UC,
 };
 
 struct i915_mmap_offset {
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 63d40cba97e0..190659923dea 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -394,7 +394,7 @@ typedef struct _drm_i915_sarea {
 #define DRM_IOCTL_I915_GEM_PREAD	DRM_IOW (DRM_COMMAND_BASE + DRM_I915_GEM_PREAD, struct drm_i915_gem_pread)
 #define DRM_IOCTL_I915_GEM_PWRITE	DRM_IOW (DRM_COMMAND_BASE + DRM_I915_GEM_PWRITE, struct drm_i915_gem_pwrite)
 #define DRM_IOCTL_I915_GEM_MMAP		DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_MMAP, struct drm_i915_gem_mmap)
-#define DRM_IOCTL_I915_GEM_MMAP_GTT	DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_MMAP_GTT, struct drm_i915_gem_mmap_gtt)
+#define DRM_IOCTL_I915_GEM_MMAP_GTT	DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_MMAP_GTT, struct drm_i915_gem_mmap_offset)
 #define DRM_IOCTL_I915_GEM_SET_DOMAIN	DRM_IOW (DRM_COMMAND_BASE + DRM_I915_GEM_SET_DOMAIN, struct drm_i915_gem_set_domain)
 #define DRM_IOCTL_I915_GEM_SW_FINISH	DRM_IOW (DRM_COMMAND_BASE + DRM_I915_GEM_SW_FINISH, struct drm_i915_gem_sw_finish)
 #define DRM_IOCTL_I915_GEM_SET_TILING	DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_SET_TILING, struct drm_i915_gem_set_tiling)
@@ -793,6 +793,31 @@ struct drm_i915_gem_mmap_gtt {
 	__u64 offset;
 };
 
+struct drm_i915_gem_mmap_offset {
+	/** Handle for the object being mapped. */
+	__u32 handle;
+	__u32 pad;
+	/**
+	 * Fake offset to use for subsequent mmap call
+	 *
+	 * This is a fixed-size type for 32/64 compatibility.
+	 */
+	__u64 offset;
+
+	/**
+	 * Flags for extended behaviour.
+	 *
+	 * It is mandatory that either one of the MMAP_OFFSET flags
+	 * should be passed here.
+	 */
+	__u64 flags;
+#define I915_MMAP_OFFSET_WC 1
+#define I915_MMAP_OFFSET_WB 2
+#define I915_MMAP_OFFSET_UC 3
+
+	__u64 extensions;
+};
+
 struct drm_i915_gem_set_domain {
 	/** Handle for the object */
 	__u32 handle;
-- 
2.23.0