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, 12 deletions

diff --git a/contrib/vhost-user-scsi/vhost-user-scsi.c b/contrib/vhost-user-scsi/vhost-user-scsi.c
index 496dd6e693..0fc14d7899 100644
--- a/contrib/vhost-user-scsi/vhost-user-scsi.c
+++ b/contrib/vhost-user-scsi/vhost-user-scsi.c
@@ -19,6 +19,10 @@
 
 #define VUS_ISCSI_INITIATOR "iqn.2016-11.com.nutanix:vhost-user-scsi"
 
+enum {
+    VHOST_USER_SCSI_MAX_QUEUES = 8,
+};
+
 typedef struct VusIscsiLun {
     struct iscsi_context *iscsi_ctx;
     int iscsi_lun;
@@ -231,11 +235,6 @@ static void vus_proc_req(VuDev *vu_dev, int idx)
 
     gdev = container_of(vu_dev, VugDev, parent);
     vdev_scsi = container_of(gdev, VusDev, parent);
-    if (idx < 0 || idx >= VHOST_MAX_NR_VIRTQUEUE) {
-        g_warning("VQ Index out of range: %d", idx);
-        vus_panic_cb(vu_dev, NULL);
-        return;
-    }
 
     vq = vu_get_queue(vu_dev, idx);
     if (!vq) {
@@ -295,12 +294,6 @@ static void vus_queue_set_started(VuDev *vu_dev, int idx, bool started)
 
     assert(vu_dev);
 
-    if (idx < 0 || idx >= VHOST_MAX_NR_VIRTQUEUE) {
-        g_warning("VQ Index out of range: %d", idx);
-        vus_panic_cb(vu_dev, NULL);
-        return;
-    }
-
     vq = vu_get_queue(vu_dev, idx);
 
     if (idx == 0 || idx == 1) {
@@ -398,7 +391,11 @@ int main(int argc, char **argv)
         goto err;
     }
 
-    vug_init(&vdev_scsi->parent, csock, vus_panic_cb, &vus_iface);
+    if (!vug_init(&vdev_scsi->parent, VHOST_USER_SCSI_MAX_QUEUES, csock,
+                  vus_panic_cb, &vus_iface)) {
+        g_printerr("Failed to initialize libvhost-user-glib\n");
+        goto err;
+    }
 
     g_main_loop_run(vdev_scsi->loop);