[libvirt] [PATCH 2/2] Add support for QEMU -add-fd support detection

[Stefan Berger]

On 01/30/2013 11:21 PM, Eric Blake wrote:
> From: Stefan Berger <stefanb at linux.vnet.ibm.com>
>
> Add support for QEMU -add-fd command line parameter detection.
> This intentionally rejects qemu 1.2, where 'add-fd' QMP did
> not allow full control of set ids, and where there was no command
> line counterpart, but accepts qemu 1.3.
>
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>
> v1 was here:
> https://www.redhat.com/archives/libvir-list/2013-January/msg02056.html
>
> Okay, so most of v2 is mine, but I kept Stefan as author for his
> contribution in adding just one capability named QEMU_CAPS_ADD_FD.
>
>   src/qemu/qemu_capabilities.c | 22 +++++++++++++++++++++-
>   src/qemu/qemu_capabilities.h |  1 +
>   2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index 29693c3..0820fe4 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -1,7 +1,7 @@
>   /*
>    * qemu_capabilities.c: QEMU capabilities generation
>    *
> - * Copyright (C) 2006-2012 Red Hat, Inc.
> + * Copyright (C) 2006-2013 Red Hat, Inc.
>    * Copyright (C) 2006 Daniel P. Berrange
>    *
>    * This library is free software; you can redistribute it and/or
> @@ -39,6 +39,7 @@
>   #include "virnodesuspend.h"
>   #include "qemu_monitor.h"
>
> +#include <fcntl.h>
>   #include <sys/stat.h>
>   #include <unistd.h>
>   #include <sys/wait.h>
> @@ -203,6 +204,7 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
>
>                 "usb-serial", /* 125 */
>                 "usb-net",
> +              "add-fd",
>
>       );
>
> @@ -1961,10 +1963,28 @@ qemuCapsProbeQMPCommands(qemuCapsPtr caps,
>               qemuCapsSet(caps, QEMU_CAPS_DRIVE_MIRROR);
>           else if (STREQ(name, "blockdev-snapshot-sync"))
>               qemuCapsSet(caps, QEMU_CAPS_DISK_SNAPSHOT);
> +        else if (STREQ(name, "add-fd"))
> +            qemuCapsSet(caps, QEMU_CAPS_ADD_FD);

This checks for QMP support -> version 1.2.

>           VIR_FREE(name);
>       }
>       VIR_FREE(commands);
>
> +    /* QMP add-fd was introduced in 1.2, but did not support
> +     * management control of set numbering, and did not have a
> +     * counterpart -add-fd command line option.  We require the
> +     * add-fd features from 1.3 or later.  */
> +    if (qemuCapsGet(caps, QEMU_CAPS_ADD_FD)) {
> +        int fd = open("/dev/null", O_RDONLY);
> +        if (fd < 0) {
> +            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                           _("unable to probe for add-fd"));
> +            return -1;
> +        }
> +        if (qemuMonitorAddFd(mon, 0, fd, "/dev/null") < 0)
> +            qemuCapsClear(caps, QEMU_CAPS_ADD_FD);
> +        VIR_FORCE_CLOSE(fd);
> +    }
> +

Aren't you only detecting version 1.2 with this?

I thought we would need something along the lines of this example here:

     if (version >= 9000)
         qemuCapsSet(caps, QEMU_CAPS_VNC_COLON);

    Stefan