[libvirt PATCH] qemu: do not attempt to pass unopened vsock FD

[Ján Tomko]

On normal vm startup, we open a file descriptor
for the vsock device in qemuProcessPrepareHost.

However, when doing domxml-to-native, no file descriptors are open.

Only pass the fd if it's not -1, to make domxml-to-native work.

https://bugzilla.redhat.com/show_bug.cgi?id=1777212

Signed-off-by: Ján Tomko <jtomko at redhat.com>
---
Technically a v2 of:
https://listman.redhat.com/archives/libvir-list/2021-July/msg00803.html

I did not look at other cases, but IIRC the ones converted to use qemuFD*
wrappers should handle missing FDs gracefully.

 src/qemu/qemu_command.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 150824f2e1..bbbde57c0f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -9717,7 +9717,8 @@ qemuBuildVsockCommandLine(virCommand *cmd,
     if (!(devprops = qemuBuildVsockDevProps(def, vsock, qemuCaps, "")))
         return -1;
 
-    virCommandPassFD(cmd, priv->vhostfd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+    if (priv->vhostfd != -1)
+        virCommandPassFD(cmd, priv->vhostfd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
     priv->vhostfd = -1;
 
     if (qemuCommandAddExtDevice(cmd, &vsock->info, def, qemuCaps) < 0)
-- 
2.37.3