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

[Peter Krempa]

On Thu, Oct 20, 2022 at 16:27:45 +0200, Ján Tomko wrote:
> 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;

In 'qemuBuildVsockDevProps' the 'fd' field is formated via '%u'. Please
change it to '%d' to go along with this patch.

>  
>      if (qemuCommandAddExtDevice(cmd, &vsock->info, def, qemuCaps) < 0)
> -- 
> 2.37.3

Reviewed-by: Peter Krempa <pkrempa at redhat.com>