virtio-gpu api: host visible feature

This patch adds a new virtgpu feature that allows directly
mapping host allocated resources.

This is based on virtio shared memory regions, which allows
querying for memory regions using PCI transport. Each shared
memory region has an associated "shmid", the meaning of which
is device specific.

For virtio-gpu, we can define the shared memory region with id
VIRTIO_GPU_SHM_ID_HOST_VISIBLE to be the "host visible memory
region".

The presence of the host visible memory region means the following
hypercalls are supported:

1) VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB

This hypercall tells the host to inject the host resource's
mapping in an offset into virtio-gpu's PCI address space.
This is typically done via KVM_SET_USER_MEMORY_REGION on Linux
hosts.

On success, VIRTIO_GPU_RESP_OK_MAP_INFO is returned, which
specifies the host buffer's caching type and possibly in the
future performance hints about the buffer..

2) VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB

This hypercall tells the host to remove the host resource's
mapping from the guest VM.

Signed-off-by: Gerd Hoffmann <[e-mail]>
Acked-by: Tomeu Vizoso <[e-mail]>
Acked-by: Lingfeng Yang <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Co-developed-by: Gurchetan Singh <[e-mail]>
Signed-off-by: Gurchetan Singh <[e-mail]>

include/uapi/linux/virtio_gpu.h

···
 	VIRTIO_GPU_CMD_TRANSFER_TO_HOST_3D,
 	VIRTIO_GPU_CMD_TRANSFER_FROM_HOST_3D,
 	VIRTIO_GPU_CMD_SUBMIT_3D,
+	VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB,
+	VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB,
 
 	/* cursor commands */
 	VIRTIO_GPU_CMD_UPDATE_CURSOR = 0x0300,
···
 	VIRTIO_GPU_RESP_OK_CAPSET,
 	VIRTIO_GPU_RESP_OK_EDID,
 	VIRTIO_GPU_RESP_OK_RESOURCE_UUID,
+	VIRTIO_GPU_RESP_OK_MAP_INFO,
 
 	/* error responses */
 	VIRTIO_GPU_RESP_ERR_UNSPEC = 0x1200,
···
 	VIRTIO_GPU_RESP_ERR_INVALID_RESOURCE_ID,
 	VIRTIO_GPU_RESP_ERR_INVALID_CONTEXT_ID,
 	VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER,
+};
+
+enum virtio_gpu_shm_id {
+	VIRTIO_GPU_SHM_ID_UNDEFINED = 0,
+	VIRTIO_GPU_SHM_ID_HOST_VISIBLE = 1
 };
 
 #define VIRTIO_GPU_FLAG_FENCE (1 << 0)
···
 	__le32 padding;
 	__le32 strides[4];
 	__le32 offsets[4];
+};
+
+/* VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB */
+struct virtio_gpu_resource_map_blob {
+	struct virtio_gpu_ctrl_hdr hdr;
+	__le32 resource_id;
+	__le32 padding;
+	__le64 offset;
+};
+
+/* VIRTIO_GPU_RESP_OK_MAP_INFO */
+#define VIRTIO_GPU_MAP_CACHE_MASK     0x0f
+#define VIRTIO_GPU_MAP_CACHE_NONE     0x00
+#define VIRTIO_GPU_MAP_CACHE_CACHED   0x01
+#define VIRTIO_GPU_MAP_CACHE_UNCACHED 0x02
+#define VIRTIO_GPU_MAP_CACHE_WC       0x03
+struct virtio_gpu_resp_map_info {
+	struct virtio_gpu_ctrl_hdr hdr;
+	__u32 map_info;
+	__u32 padding;
+};
+
+/* VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB */
+struct virtio_gpu_resource_unmap_blob {
+	struct virtio_gpu_ctrl_hdr hdr;
+	__le32 resource_id;
+	__le32 padding;
 };
 
 #endif