vhost-user: modify SET_LOG_BASE to pass mmap size and offset

Unlike the kernel, vhost-user application accesses log table by
mmaping it to its user space. This change adds two new fields to
VhostUserMsg payload: mmap_size, and mmap_offset and make QEMU to
pass the to vhost-user application in VHOST_USER_SET_LOG_BASE
request.

Signed-off-by: Victor Kaplansky <victork@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

docs/specs/vhost-user.txt

@@ -98,6 +98,7 @@ typedef struct VhostUserMsg {
         struct vhost_vring_state state;
         struct vhost_vring_addr addr;
         VhostUserMemory memory;
+        VhostUserLog log;
     };
 } QEMU_PACKED VhostUserMsg;
 
@@ -282,7 +283,12 @@ Message types
       Master payload: u64
       Slave payload: N/A
 
-      Sets the logging base address.
+      Sets logging shared memory space.
+      When slave has VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol
+      feature, the log memory fd is provided in the ancillary data of
+      VHOST_USER_SET_LOG_BASE message, the size and offset of shared
+      memory area provided in the message.
+
 
  * VHOST_USER_SET_LOG_FD
 

hw/virtio/vhost-user.c

@@ -75,6 +75,11 @@ typedef struct VhostUserMemory {
     VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
 } VhostUserMemory;
 
+typedef struct VhostUserLog {
+    uint64_t mmap_size;
+    uint64_t mmap_offset;
+} VhostUserLog;
+
 typedef struct VhostUserMsg {
     VhostUserRequest request;
 
@@ -89,6 +94,7 @@ typedef struct VhostUserMsg {
         struct vhost_vring_state state;
         struct vhost_vring_addr addr;
         VhostUserMemory memory;
+        VhostUserLog log;
     } payload;
 } QEMU_PACKED VhostUserMsg;
 
@@ -200,8 +206,9 @@ static int vhost_user_set_log_base(struct vhost_dev *dev, uint64_t base,
     VhostUserMsg msg = {
         .request = VHOST_USER_SET_LOG_BASE,
         .flags = VHOST_USER_VERSION,
-        .payload.u64 = base,
-        .size = sizeof(msg.payload.u64),
+        .payload.log.mmap_size = log->size,
+        .payload.log.mmap_offset = 0,
+        .size = sizeof(msg.payload.log),
     };
 
     if (shmfd && log->fd != -1) {

tests/vhost-user-test.c

@@ -86,6 +86,11 @@ typedef struct VhostUserMemory {
     VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
 } VhostUserMemory;
 
+typedef struct VhostUserLog {
+    uint64_t mmap_size;
+    uint64_t mmap_offset;
+} VhostUserLog;
+
 typedef struct VhostUserMsg {
     VhostUserRequest request;
 
@@ -94,10 +99,13 @@ typedef struct VhostUserMsg {
     uint32_t flags;
     uint32_t size; /* the following payload size */
     union {
+#define VHOST_USER_VRING_IDX_MASK   (0xff)
+#define VHOST_USER_VRING_NOFD_MASK  (0x1<<8)
         uint64_t u64;
         struct vhost_vring_state state;
         struct vhost_vring_addr addr;
         VhostUserMemory memory;
+        VhostUserLog log;
     } payload;
 } QEMU_PACKED VhostUserMsg;