[PATCH 3/5] drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET

Abdiel Janulgue
2019-10-23T08:30:41Z

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@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@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..69779eca6309 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 (!i915_ggtt_has_aperture(&i915->ggtt))
+ /* 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;