[libvirt] [PATCH] Fix bug of attaching redirdev device

[Michal Privoznik]

On 18.02.2016 17:02, Osier Yang wrote:
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1298070
> 

Hey! It's nice to see people returning :)

> The corresponding chardev must be attached first, otherwise the
> the qemu command line won't be complete (missing the host part),
> ---
>  src/qemu/qemu_hotplug.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index ee305e7..5095e31 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -1381,6 +1381,7 @@ int qemuDomainAttachRedirdevDevice(virQEMUDriverPtr driver,
>      int ret;
>      qemuDomainObjPrivatePtr priv = vm->privateData;
>      virDomainDefPtr def = vm->def;
> +    char *charAlias = NULL;
>      char *devstr = NULL;
>  
>      if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
> @@ -1391,21 +1392,33 @@ int qemuDomainAttachRedirdevDevice(virQEMUDriverPtr driver,
>  
>      if (qemuAssignDeviceRedirdevAlias(vm->def, redirdev, -1) < 0)
>          goto error;
> -    if (!(devstr = qemuBuildRedirdevDevStr(def, redirdev, priv->qemuCaps)))
> -        goto error;
>  
> -    if (VIR_REALLOC_N(vm->def->redirdevs, vm->def->nredirdevs+1) < 0)
> +    if (virAsprintf(&charAlias, "char%s", redirdev->info.alias) < 0)
>          goto error;
>  
>      qemuDomainObjEnterMonitor(driver, vm);
> +    if (qemuMonitorAttachCharDev(priv->mon,
> +                                 charAlias,
> +                                 &(redirdev->source.chr)) < 0) {
> +        ignore_value(qemuDomainObjExitMonitor(driver, vm));
> +        goto error;
> +    }
> +    VIR_FREE(charAlias);
> +
> +    if (!(devstr = qemuBuildRedirdevDevStr(def, redirdev, priv->qemuCaps)))
> +        goto rollback;
> +
> +    if (VIR_REALLOC_N(vm->def->redirdevs, vm->def->nredirdevs+1) < 0)
> +        goto rollback;
> +
>      ret = qemuMonitorAddDevice(priv->mon, devstr);
>  
>      if (qemuDomainObjExitMonitor(driver, vm) < 0)
> -        goto error;
> +        goto rollback;

This usually means that domain died meanwhile, so there's no need for
performing rollback. It will fail anyway.

>  
>      virDomainAuditRedirdev(vm, redirdev, "attach", ret == 0);
>      if (ret < 0)
> -        goto error;
> +        goto rollback;

This would end up calling a monitor command without corresponding
Enter/ExitMonitor guards.

Moreover, I think the time spent in monitor should be the shortest
possible. Therefore all the preparation (e.g. allocation) should be done
upfront, before entering monitor. I think I see a way how to achieve
that. Would you mind rewriting that? If rewritten wisely no rollback
label should be needed.

>  
>      vm->def->redirdevs[vm->def->nredirdevs++] = redirdev;
>  
> @@ -1414,9 +1427,13 @@ int qemuDomainAttachRedirdevDevice(virQEMUDriverPtr driver,
>      return 0;
>  
>   error:
> +    VIR_FREE(charAlias);
>      VIR_FREE(devstr);
>      return -1;
>  
> + rollback:
> +    ignore_value(qemuMonitorDetachCharDev(priv->mon, charAlias));
> +    goto error;
>  }
>  
>  static int
> 

Michal