From: Marc-André Lureau <marcandre.lur...@redhat.com>
Learn to give a socket to the slave to let him make requests to the
master.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
docs/specs/vhost-user.txt | 23 ++++++++++++++++
hw/virtio/vhost-user.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 92 insertions(+)
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 0312d40..8a635fa 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -248,12 +248,25 @@ Once the source has finished migration, rings will be
stopped by
the source. No further update must be done before rings are
restarted.
+Slave communication
+-------------------
+
+An optional communication channel is provided if the slave
+declares VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL feature, to allow
+the slave to make requests to the master.
+
+The fd is provided via VHOST_USER_SET_SLAVE_FD ancillary data.
+
+A slave may then send VHOST_USER_SLAVE_* messages to the master
+using this fd communication channel.
+
Protocol features
-----------------
#define VHOST_USER_PROTOCOL_F_MQ 0
#define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1
#define VHOST_USER_PROTOCOL_F_RARP 2
+#define VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL 3
Message types
-------------
@@ -464,3 +477,13 @@ Message types
is present in VHOST_USER_GET_PROTOCOL_FEATURES.
The first 6 bytes of the payload contain the mac address of the guest to
allow the vhost user backend to construct and broadcast the fake RARP.
+
+ * VHOST_USER_SET_SLAVE_FD
+ Id: 20
+ Equivalent ioctl: N/A
+ Master payload: N/A
+
+ Set the file descriptor for the salve to make VHOST_USER_SLAVE_*
+ request to the master. It is passed in the ancillary data.
+ This message is only sent if VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL
+ feature is available.
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 02ac1fc..890c1bd 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -32,6 +32,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_MQ = 0,
VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
VHOST_USER_PROTOCOL_F_RARP = 2,
+ VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL = 3,
VHOST_USER_PROTOCOL_F_MAX
};
@@ -59,9 +60,16 @@ typedef enum VhostUserRequest {
VHOST_USER_GET_QUEUE_NUM = 17,
VHOST_USER_SET_VRING_ENABLE = 18,
VHOST_USER_SEND_RARP = 19,
+ VHOST_USER_SET_SLAVE_FD = 20,
+
VHOST_USER_MAX
} VhostUserRequest;
+typedef enum VhostUserSlaveRequest {
+ VHOST_USER_SLAVE_NONE = 0,
+ VHOST_USER_SLAVE_MAX
+} VhostUserSlaveRequest;
+
typedef struct VhostUserMemoryRegion {
uint64_t guest_phys_addr;
uint64_t memory_size;
@@ -110,6 +118,7 @@ static VhostUserMsg m __attribute__ ((unused));
struct vhost_user {
CharDriverState *chr;
+ int slave_fd;
};
static bool ioeventfd_enabled(void)
@@ -513,6 +522,55 @@ static int vhost_user_reset_device(struct vhost_dev *dev)
return 0;
}
+static void slave_read(void *opaque)
+{
+ struct vhost_dev *dev = opaque;
+ struct vhost_user *u = dev->opaque;
+ VhostUserMsg msg = { 0, };
+ int size;
+
+ size = read(u->slave_fd, &msg, VHOST_USER_HDR_SIZE);
+ if (size != VHOST_USER_HDR_SIZE) {
+ error_report("Failed to read from slave.");
+ qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
+ close(u->slave_fd);
+ u->slave_fd = -1;
+ return;
+ }
+
+ switch (msg.request) {
+ default:
+ error_report("Received unexpected msg type.");
+ }
+}
+
+static int vhost_setup_slave_channel(struct vhost_dev *dev)
+{
+ VhostUserMsg msg = {
+ .request = VHOST_USER_SET_SLAVE_FD,
+ .flags = VHOST_USER_VERSION,
+ };
+ struct vhost_user *u = dev->opaque;
+ int sv[2];
+
+ if (!virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_SLAVE_CHANNEL)) {
+ return 0;
+ }
+
+ if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) {
+ error_report("socketpair() failed");
+ return -1;
+ }
+
+ u->slave_fd = sv[0];
+ qemu_set_fd_handler(u->slave_fd, slave_read, NULL, dev);
+
+ vhost_user_write(dev, &msg, &sv[1], 1);
+
+ return 0;
+}
+
static int vhost_user_init(struct vhost_dev *dev, void *opaque)
{
uint64_t features;
@@ -523,6 +581,7 @@ static int vhost_user_init(struct vhost_dev *dev, void
*opaque)
u = g_new0(struct vhost_user, 1);
u->chr = opaque;
+ u->slave_fd = -1;
dev->opaque = u;
err = vhost_user_get_features(dev, &features);
@@ -563,6 +622,12 @@ static int vhost_user_init(struct vhost_dev *dev, void
*opaque)
"VHOST_USER_PROTOCOL_F_LOG_SHMFD feature.");
}
+
+ err = vhost_setup_slave_channel(dev);
+ if (err < 0) {
+ return err;
+ }
+
return 0;
}
@@ -573,6 +638,10 @@ static int vhost_user_cleanup(struct vhost_dev *dev)
assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
u = dev->opaque;
+ if (u->slave_fd >= 0) {
+ close(u->slave_fd);
+ u->slave_fd = -1;
+ }
g_free(u);
dev->opaque = 0;
--
2.5.5
