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, 28 insertions, 14 deletions

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index 0bb03af0e5..c4e350e1f5 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -45,6 +45,10 @@
         } \
     } while (0)
 
+enum {
+    VHOST_USER_BRIDGE_MAX_QUEUES = 8,
+};
+
 typedef void (*CallbackFunc)(int sock, void *ctx);
 
 typedef struct Event {
@@ -512,12 +516,16 @@ vubr_accept_cb(int sock, void *ctx)
     }
     DPRINT("Got connection from remote peer on sock %d\n", conn_fd);
 
-    vu_init(&dev->vudev,
-            conn_fd,
-            vubr_panic,
-            vubr_set_watch,
-            vubr_remove_watch,
-            &vuiface);
+    if (!vu_init(&dev->vudev,
+                 VHOST_USER_BRIDGE_MAX_QUEUES,
+                 conn_fd,
+                 vubr_panic,
+                 vubr_set_watch,
+                 vubr_remove_watch,
+                 &vuiface)) {
+        fprintf(stderr, "Failed to initialize libvhost-user\n");
+        exit(1);
+    }
 
     dispatcher_add(&dev->dispatcher, conn_fd, ctx, vubr_receive_cb);
     dispatcher_remove(&dev->dispatcher, sock);
@@ -560,12 +568,18 @@ vubr_new(const char *path, bool client)
         if (connect(dev->sock, (struct sockaddr *)&un, len) == -1) {
             vubr_die("connect");
         }
-        vu_init(&dev->vudev,
-                dev->sock,
-                vubr_panic,
-                vubr_set_watch,
-                vubr_remove_watch,
-                &vuiface);
+
+        if (!vu_init(&dev->vudev,
+                     VHOST_USER_BRIDGE_MAX_QUEUES,
+                     dev->sock,
+                     vubr_panic,
+                     vubr_set_watch,
+                     vubr_remove_watch,
+                     &vuiface)) {
+            fprintf(stderr, "Failed to initialize libvhost-user\n");
+            exit(1);
+        }
+
         cb = vubr_receive_cb;
     }
 
@@ -584,7 +598,7 @@ static void *notifier_thread(void *arg)
     int qidx;
 
     while (true) {
-        for (qidx = 0; qidx < VHOST_MAX_NR_VIRTQUEUE; qidx++) {
+        for (qidx = 0; qidx < VHOST_USER_BRIDGE_MAX_QUEUES; qidx++) {
             uint16_t *n = vubr->notifier.addr + pagesize * qidx;
 
             if (*n == qidx) {
@@ -616,7 +630,7 @@ vubr_host_notifier_setup(VubrDev *dev)
     void *addr;
     int fd;
 
-    length = getpagesize() * VHOST_MAX_NR_VIRTQUEUE;
+    length = getpagesize() * VHOST_USER_BRIDGE_MAX_QUEUES;
 
     fd = mkstemp(template);
     if (fd < 0) {