vhost-user: send log shm fd along with log_base

Send the shm for the dirty pages logging if the backend supports
VHOST_USER_PROTOCOL_F_LOG_SHMFD. Wait for a reply to make sure
the old log is no longer used.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Thibaut Collet <thibaut.collet@6wind.com>

3 files changed, 30 insertions, 5 deletions

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 5846c37f6d..5a2f1af137 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -67,7 +67,8 @@ static int vhost_kernel_memslots_limit(struct vhost_dev *dev)
     return limit;
 }
 
-static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
+static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base,
+                              struct vhost_log *log)
 {
     return vhost_kernel_call(dev, VHOST_SET_LOG_BASE, &base);
 }
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index e10ce87299..2709c4ee39 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -367,8 +367,13 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
     return 0;
 }
 
-static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
+static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base,
+                              struct vhost_log *log)
 {
+    int fds[VHOST_MEMORY_MAX_NREGIONS];
+    size_t fd_num = 0;
+    bool shmfd = virtio_has_feature(dev->protocol_features,
+                                    VHOST_USER_PROTOCOL_F_LOG_SHMFD);
     VhostUserMsg msg = {
         .request = VHOST_USER_SET_LOG_BASE,
         .flags = VHOST_USER_VERSION,
@@ -376,7 +381,25 @@ static int vhost_set_log_base(struct vhost_dev *dev, uint64_t base)
         .size = sizeof(m.u64),
     };
 
-    vhost_user_write(dev, &msg, NULL, 0);
+    if (shmfd && log->fd != -1) {
+        fds[fd_num++] = log->fd;
+    }
+
+    vhost_user_write(dev, &msg, fds, fd_num);
+
+    if (shmfd) {
+        msg.size = 0;
+        if (vhost_user_read(dev, &msg) < 0) {
+            return 0;
+        }
+
+        if (msg.request != VHOST_USER_SET_LOG_BASE) {
+            error_report("Received unexpected msg type. "
+                         "Expected %d received %d",
+                         VHOST_USER_SET_LOG_BASE, msg.request);
+            return -1;
+        }
+    }
 
     return 0;
 }
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index aec92d4691..65c09bf888 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -388,7 +388,7 @@ static inline void vhost_dev_log_resize(struct vhost_dev *dev, uint64_t size)
 
     /* inform backend of log switching, this must be done before
        releasing the current log, to ensure no logging is lost */
-    r = dev->vhost_ops->vhost_set_log_base(dev, log_base);
+    r = dev->vhost_ops->vhost_set_log_base(dev, log_base, log);
     assert(r >= 0);
     vhost_log_put(dev, true);
     dev->log = log;
@@ -1205,7 +1205,8 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
                                   vhost_dev_log_is_shared(hdev));
         log_base = (uintptr_t)hdev->log->log;
         r = hdev->vhost_ops->vhost_set_log_base(hdev,
-                                                hdev->log_size ? log_base : 0);
+                                                hdev->log_size ? log_base : 0,
+                                                hdev->log);
         if (r < 0) {
             r = -errno;
             goto fail_log;