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libvhost-user: implement VHOST_USER_PROTOCOL_F_MQ

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Existing vhost-user device backends, including vhost-user-scsi and
vhost-user-blk, support multiqueue but libvhost-user currently does not
advertise this.

VHOST_USER_PROTOCOL_F_MQ enables the VHOST_USER_GET_QUEUE_NUM request
needed for a vhost-user master to query the number of queues.  For
example, QEMU's vhost-user-net master depends on
VHOST_USER_PROTOCOL_F_MQ for multiqueue.

If you're wondering how any device backend with more than one virtqueue
functions today, it's because device types with a fixed number of
virtqueues do not require querying the number of queues.  Therefore the
vhost-user master for vhost-user-input with 2 virtqueues, for example,
doesn't actually depend on VHOST_USER_PROTOCOL_F_MQ.  It just enables
virtqueues 0 and 1 without asking.

Let there be multiqueue!

Suggested-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190626074815.19994-4-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2019-06-26 08:48:14 +01:00 committed by Michael S. Tsirkin
parent 6f5fd83788
commit ea1b802ca2
1 changed files with 4 additions and 3 deletions
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7
contrib/libvhost-user/libvhost-user.c
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@ -1160,7 +1160,8 @@ vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg)
static bool
vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
{
uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD |
uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_MQ |
1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD |
1ULL << VHOST_USER_PROTOCOL_F_SLAVE_REQ |
1ULL << VHOST_USER_PROTOCOL_F_HOST_NOTIFIER |
1ULL << VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD;
@ -1200,8 +1201,8 @@ vu_set_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
static bool
vu_get_queue_num_exec(VuDev *dev, VhostUserMsg *vmsg)
{
DPRINT("Function %s() not implemented yet.\n", __func__);
return false;
vmsg_set_reply_u64(vmsg, dev->max_queues);
return true;
}
static bool