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Re: [libvirt] [PATCH] qemu: Issue rtc_reset_reinjection command after guest-set-time



On 08/13/2014 06:51 AM, Michal Privoznik wrote:

s/_/-/2 in the subject line

> An advice appeared there on the qemu-devel list [1]. When a domain is
> suspended and then resumed guest kernel is not aware of this. So we've
> introduced virDomainSetTime API that resets the time within guest
> using qemu-ga. On the other hand, qemu itself is trying to make RTC
> beat faster to catch the difference. But if we don't tell qemu that
> guest's time was reset via the other method, both mechanisms are
> applied resulting in again wrong guest time. In order to avoid summing
> both corrections we need to tell qemu that it should not use the RTC
> injection if the guest time is set via guest agent.
> 
> 1: http://www.mail-archive.com/qemu-devel nongnu org/msg236435.html
> 
> Signed-off-by: Michal Privoznik <mprivozn redhat com>
> ---

> +++ b/src/qemu/qemu_driver.c
> @@ -16879,6 +16879,16 @@ qemuDomainSetTime(virDomainPtr dom,
>      rv = qemuAgentSetTime(priv->agent, seconds, nseconds, rtcSync);
>      qemuDomainObjExitAgent(vm);
>  
> +    if (!virDomainObjIsActive(vm)) {
> +        virReportError(VIR_ERR_OPERATION_INVALID,
> +                       "%s", _("domain is not running"));
> +        goto endjob;
> +    }
> +
> +    qemuDomainObjEnterMonitor(driver, vm);
> +    rv = qemuMonitorRTCResetReinjection(priv->mon);
> +    qemuDomainObjExitMonitor(driver, vm);

This forces the command to fail if qemu is too old to have
rtc-reset-reinjection but the agent is new enough to set time.  Should
you make this code conditional on whether qemu supports the QMP command?


>  }
> +
> +int
> +qemuMonitorJSONRTCResetReinjection(qemuMonitorPtr mon)
> +{
> +    int ret = -1;
> +    virJSONValuePtr cmd;
> +    virJSONValuePtr reply = NULL;
> +
> +    if (!(cmd = qemuMonitorJSONMakeCommand("rtc-reset-reinjection",
> +                                           NULL)))
> +        return ret;
> +
> +    ret = qemuMonitorJSONCommand(mon, cmd, &reply);
> +
> +    if (ret == 0)
> +        ret = qemuMonitorJSONCheckError(cmd, reply);
> +
> +    virJSONValueFree(cmd);
> +    virJSONValueFree(reply);
> +    return ret;
> +}

Is it worth enhancing the testsuite to add coverage for this command and
expected response?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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