libvhost-user: support many virtqueues

Currently libvhost-user is hardcoded to at most 8 virtqueues.  The
device backend should decide the number of virtqueues, not
libvhost-user.  This is important for multiqueue device backends where
the guest driver needs an accurate number of virtqueues.

This change breaks libvhost-user and libvhost-user-glib API stability.
There is no stability guarantee yet, so make this change now and update
all in-tree library users.

This patch touches up vhost-user-blk, vhost-user-gpu, vhost-user-input,
vhost-user-scsi, and vhost-user-bridge.  If the device has a fixed
number of queues that exact number is used.  Otherwise the previous
default of 8 virtqueues is used.

vu_init() and vug_init() can now fail if malloc() returns NULL.  I
considered aborting with an error in libvhost-user but it should be safe
to instantiate new vhost-user instances at runtime without risk of
terminating the process.  Therefore callers need to handle the vu_init()
failure now.

vhost-user-blk and vhost-user-scsi duplicate virtqueue index checks that
are already performed by libvhost-user.  This code would need to be
modified to use max_queues but remove it completely instead since it's
redundant.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190626074815.19994-3-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/contrib/vhost-user-blk/vhost-user-blk.c b/contrib/vhost-user-blk/vhost-user-blk.c
index 86a3987744..ae61034656 100644
--- a/contrib/vhost-user-blk/vhost-user-blk.c
+++ b/contrib/vhost-user-blk/vhost-user-blk.c
@@ -25,6 +25,10 @@
 #include <sys/ioctl.h>
 #endif
 
+enum {
+    VHOST_USER_BLK_MAX_QUEUES = 8,
+};
+
 struct virtio_blk_inhdr {
     unsigned char status;
 };
@@ -334,12 +338,6 @@ static void vub_process_vq(VuDev *vu_dev, int idx)
     VuVirtq *vq;
     int ret;
 
-    if ((idx < 0) || (idx >= VHOST_MAX_NR_VIRTQUEUE)) {
-        fprintf(stderr, "VQ Index out of range: %d\n", idx);
-        vub_panic_cb(vu_dev, NULL);
-        return;
-    }
-
     gdev = container_of(vu_dev, VugDev, parent);
     vdev_blk = container_of(gdev, VubDev, parent);
     assert(vdev_blk);
@@ -631,7 +629,11 @@ int main(int argc, char **argv)
         vdev_blk->enable_ro = true;
     }
 
-    vug_init(&vdev_blk->parent, csock, vub_panic_cb, &vub_iface);
+    if (!vug_init(&vdev_blk->parent, VHOST_USER_BLK_MAX_QUEUES, csock,
+                  vub_panic_cb, &vub_iface)) {
+        fprintf(stderr, "Failed to initialized libvhost-user-glib\n");
+        goto err;
+    }
 
     g_main_loop_run(vdev_blk->loop);