[libvirt] [PATCH] qemu: Don't fail qemuProcessAttach for IOThreads if no JSON

[Daniel P. Berrange]

On Wed, Sep 17, 2014 at 03:07:47PM -0400, John Ferlan wrote:
> While doing some investigation for another bug I found that I could
> not qemu-attach to the process and got the following:
> 
>    error: Operation not supported: JSON monitor is required
> 
> while running thru qemuProcessAttach. Since we can only get the data
> using the JSON parser and if the guest to be attached to doesn't have
> it we shouldn't just fail. See example in virsh qemu-attach for sample
> command that failed.

It isn't simply qemu-attach that's affected. If you merely try to
start a guest normally with a QEMU that predates JSON support this
would fail too.

> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
> 
> I also considered removing the call from qemuProcessAttach rather than
> this approach.
> 
>  src/qemu/qemu_monitor.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> index 8927dbb..4342088 100644
> --- a/src/qemu/qemu_monitor.c
> +++ b/src/qemu/qemu_monitor.c
> @@ -4112,11 +4112,9 @@ qemuMonitorGetIOThreads(qemuMonitorPtr mon,
>          return -1;
>      }
>  
> -    if (!mon->json) {
> -        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> -                       _("JSON monitor is required"));
> -        return -1;
> -    }
> +    /* Requires JSON to make the query */
> +    if (!mon->json)
> +        return 0;

I think you need should do '*iothreads = NULL' for safety too.

Regards,
Daniel
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