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Re: [libvirt] [PATCH] qemu: Set domain def as updated and transient if changes

On 12/06/2010 05:35 AM, Osier Yang wrote:
> As qemu driver doesn't allow to make changes on persistent
> domain configuration via "attach/detach/update device",

However, this feature has been requested [1] - how easy will it be to
add that support after this patch is applied?

[1] https://bugzilla.redhat.com/show_bug.cgi?id=658713

> and all the changes made on the running domain configuration
> should not be persistent across next boot (without the need
> of restarting libvirtd), so:
>  1) Set the running domain def as transient, and restore
>     the domain configuration to original configuration when
>     shutdown.
>  2) Set the running domain def as updated, and reset it as
>     not updated when shutdown.
> Also for "live VCPU set", it doesn't change the persistent
> domain configuration, so, we also set the running domain
> def as updated and transient, and restore the original def
> when shutdown.
> @@ -6353,6 +6360,17 @@ qemudDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
>      if (flags & VIR_DOMAIN_VCPU_CONFIG)
>          ret = virDomainSaveConfig(driver->configDir, persistentDef);
> +    if (flags & VIR_DOMAIN_VCPU_LIVE) {
> +        /* Set running domain def as updated */
> +        if (ret == 0) {
> +            vm->updated = 1;
> +
> +            if (virDomainObjSetDefTransient(driver->caps, vm) < 0)
> +                VIR_ERROR("Unable to set domain %s's running config as transient",
> +                          vm->def->name);
> +        }
> +    }

In all of these cases, you issue VIR_ERROR but don't change the return
status.  Is that intentional, or should we make the overall API fail if
we can't create the transient counterpart?

And depending on the answer to that question, should we be attempting
the virDomainObjSetDefTransient sooner, so as to guarantee that we have
the transient counterpart prior to making any attempt to change the
running domain, so that we don't have to worry about rolling back
changes as part of returning failure?

Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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