um: drivers: Add virtio vhost-user driver

This module allows virtio devices to be used over a vhost-user socket.

Signed-off-by: Erel Geron <erelx.geron@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/Kconfig

@@ -335,3 +335,10 @@ config UML_NET_SLIRP
 	  Startup example: "eth0=slirp,FE:FD:01:02:03:04,/usr/local/bin/slirp"
 
 endmenu
+
+config VIRTIO_UML
+	tristate "UML driver for virtio devices"
+	select VIRTIO
+	help
+	  This driver provides support for virtio based paravirtual device
+	  drivers over vhost-user sockets.

arch/um/drivers/Makefile

@@ -61,6 +61,7 @@ obj-$(CONFIG_XTERM_CHAN) += xterm.o xterm_kern.o
 obj-$(CONFIG_UML_WATCHDOG) += harddog.o
 obj-$(CONFIG_BLK_DEV_COW_COMMON) += cow_user.o
 obj-$(CONFIG_UML_RANDOM) += random.o
+obj-$(CONFIG_VIRTIO_UML) += virtio_uml.o
 
 # pcap_user.o must be added explicitly.
 USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o pcap_user.o vde_user.o vector_user.o

arch/um/drivers/vhost_user.h

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Vhost-user protocol */
+
+#ifndef __VHOST_USER_H__
+#define __VHOST_USER_H__
+
+/* Message flags */
+#define VHOST_USER_FLAG_REPLY		BIT(2)
+/* Feature bits */
+#define VHOST_USER_F_PROTOCOL_FEATURES	30
+/* Protocol feature bits */
+#define VHOST_USER_PROTOCOL_F_CONFIG	9
+/* Vring state index masks */
+#define VHOST_USER_VRING_INDEX_MASK	0xff
+#define VHOST_USER_VRING_POLL_MASK	BIT(8)
+
+/* Supported version */
+#define VHOST_USER_VERSION		1
+/* Supported transport features */
+#define VHOST_USER_SUPPORTED_F		BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)
+/* Supported protocol features */
+#define VHOST_USER_SUPPORTED_PROTOCOL_F	BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG)
+
+enum vhost_user_request {
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SEND_MTU = 20,
+	VHOST_USER_SET_SLAVE_REQ_FD = 21,
+	VHOST_USER_IOTLB_MSG = 22,
+	VHOST_USER_SET_VRING_ENDIAN = 23,
+	VHOST_USER_GET_CONFIG = 24,
+	VHOST_USER_SET_CONFIG = 25,
+};
+
+struct vhost_user_header {
+	u32 request; /* Use enum vhost_user_request */
+	u32 flags;
+	u32 size;
+} __packed;
+
+struct vhost_user_config {
+	u32 offset;
+	u32 size;
+	u32 flags;
+	u8 payload[0]; /* Variable length */
+} __packed;
+
+struct vhost_user_vring_state {
+	u32 index;
+	u32 num;
+} __packed;
+
+struct vhost_user_vring_addr {
+	u32 index;
+	u32 flags;
+	u64 desc, used, avail, log;
+} __packed;
+
+struct vhost_user_mem_region {
+	u64 guest_addr;
+	u64 size;
+	u64 user_addr;
+	u64 mmap_offset;
+} __packed;
+
+struct vhost_user_mem_regions {
+	u32 num;
+	u32 padding;
+	struct vhost_user_mem_region regions[2]; /* Currently supporting 2 */
+} __packed;
+
+union vhost_user_payload {
+	u64 integer;
+	struct vhost_user_config config;
+	struct vhost_user_vring_state vring_state;
+	struct vhost_user_vring_addr vring_addr;
+	struct vhost_user_mem_regions mem_regions;
+};
+
+struct vhost_user_msg {
+	struct vhost_user_header header;
+	union vhost_user_payload payload;
+} __packed;
+
+#endif