[Qemu-devel] [PATCH] libvhost-user: handle NOFD flag in call/kick/err better

[Johannes Berg]

From: Johannes Berg <johannes.b...@intel.com>

The code here is odd, for example will it print out invalid
file descriptor numbers that were never sent in the message.

Clean that up a bit so it's actually possible to implement
a device that uses polling.

Signed-off-by: Johannes Berg <johannes.b...@intel.com>
---
 contrib/libvhost-user/libvhost-user.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/contrib/libvhost-user/libvhost-user.c 
b/contrib/libvhost-user/libvhost-user.c
index f1677da21201..17b7833d1f6b 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -920,6 +920,7 @@ static bool
 vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
 {
     int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
 
     if (index >= dev->max_queues) {
         vmsg_close_fds(vmsg);
@@ -927,8 +928,12 @@ vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
         return false;
     }
 
-    if (vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK ||
-        vmsg->fd_num != 1) {
+    if (nofd) {
+        vmsg_close_fds(vmsg);
+        return true;
+    }
+
+    if (vmsg->fd_num != 1) {
         vmsg_close_fds(vmsg);
         vu_panic(dev, "Invalid fds in request: %d", vmsg->request);
         return false;
@@ -1025,6 +1030,7 @@ static bool
 vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
 {
     int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
 
     DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
 
@@ -1038,8 +1044,8 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
         dev->vq[index].kick_fd = -1;
     }
 
-    dev->vq[index].kick_fd = vmsg->fds[0];
-    DPRINT("Got kick_fd: %d for vq: %d\n", vmsg->fds[0], index);
+    dev->vq[index].kick_fd = nofd ? -1 : vmsg->fds[0];
+    DPRINT("Got kick_fd: %d for vq: %d\n", dev->vq[index].kick_fd, index);
 
     dev->vq[index].started = true;
     if (dev->iface->queue_set_started) {
@@ -1116,6 +1122,7 @@ static bool
 vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
 {
     int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
 
     DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
 
@@ -1128,14 +1135,14 @@ vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
         dev->vq[index].call_fd = -1;
     }
 
-    dev->vq[index].call_fd = vmsg->fds[0];
+    dev->vq[index].call_fd = nofd ? -1 : vmsg->fds[0];
 
     /* in case of I/O hang after reconnecting */
-    if (eventfd_write(vmsg->fds[0], 1)) {
+    if (dev->vq[index].call_fd != -1 && eventfd_write(vmsg->fds[0], 1)) {
         return -1;
     }
 
-    DPRINT("Got call_fd: %d for vq: %d\n", vmsg->fds[0], index);
+    DPRINT("Got call_fd: %d for vq: %d\n", dev->vq[index].call_fd, index);
 
     return false;
 }
@@ -1144,6 +1151,7 @@ static bool
 vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg)
 {
     int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
 
     DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
 
@@ -1156,7 +1164,7 @@ vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg)
         dev->vq[index].err_fd = -1;
     }
 
-    dev->vq[index].err_fd = vmsg->fds[0];
+    dev->vq[index].err_fd = nofd ? -1 : vmsg->fds[0];
 
     return false;
 }
-- 
2.20.1