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Re: [libvirt] [PATCH] qemu: Implement DomainPMSuspendForDuration



On 02/08/2012 07:27 AM, Michal Privoznik wrote:
> via user agent.
> ---
>  src/qemu/qemu_agent.c  |   31 +++++++++++++++++++
>  src/qemu/qemu_agent.h  |    2 +
>  src/qemu/qemu_driver.c |   78 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 111 insertions(+), 0 deletions(-)
> 

> +
> +int
> +qemuAgentSuspend(qemuAgentPtr mon,
> +                 unsigned int target)
> +{
> +    int ret = -1;
> +    virJSONValuePtr cmd;
> +    virJSONValuePtr reply = NULL;
> +
> +    cmd = qemuAgentMakeCommand(qemuAgentSuspendModeTypeToString(target),
> +                               NULL);
> +    if (!cmd)
> +        return -1;
> +
> +    ret = qemuAgentCommand(mon, cmd, &reply);

If we are running qemu 1.0 and guest agent 1.0, a request to suspend
will be rejected (the guest agent doesn't know the command).  If we are
running qemu 1.1 and guest agent 1.1, a request to suspend should just
work.  But if we are running qemu 1.0 and guest agent 1.1, the command
will suspend the guest, but we then have no way to wake it up.

I don't think qemu_agent is the right place to check this, rather...

> +static int
> +qemuDomainPMSuspendForDuration(virDomainPtr dom,
> +                               unsigned int target,
> +                               unsigned long long duration,
> +                               unsigned int flags)
> +{
> +    struct qemud_driver *driver = dom->conn->privateData;
> +    qemuDomainObjPrivatePtr priv;
> +    virDomainObjPtr vm;
> +    int ret = -1;
> +
> +    virCheckFlags(0, -1);
> +
> +    if (duration) {
> +        qemuReportError(VIR_ERR_INVALID_ARG, "%s",
> +                        _("Duration not supported. Use 0 for now"));
> +        return -1;
> +    }
> +
> +    if (!(target == VIR_NODE_SUSPEND_TARGET_MEM ||
> +          target == VIR_NODE_SUSPEND_TARGET_DISK ||
> +          target == VIR_NODE_SUSPEND_TARGET_HYBRID)) {
> +        qemuReportError(VIR_ERR_INVALID_ARG,
> +                        _("Unknown suspend target: %u"),
> +                        target);
> +        return -1;
> +    }
> +
> +    qemuDriverLock(driver);
> +    vm = virDomainFindByUUID(&driver->domains, dom->uuid);
> +    qemuDriverUnlock(driver);
> +
> +    if (!vm) {
> +        char uuidstr[VIR_UUID_STRING_BUFLEN];
> +        virUUIDFormat(dom->uuid, uuidstr);
> +        qemuReportError(VIR_ERR_NO_DOMAIN,
> +                        _("no domain with matching uuid '%s'"), uuidstr);
> +        goto cleanup;
> +    }

...Here, after we've determined the vm, and thus the capabilities of the
gemu running the vm, we should be checking for the QEMU_CAPS of whether
the qemu is known to support wakeup.  If wakeup is not supported (qemu
1.0), then we must reject TARGET_MEM and TARGET_HYBRID at this point;
rather than calling an agent command that might succeed but get the
guest wedged into a suspended state with no recovery.

I'm also wondering if we need a new command to wake a guest that is in
S3 mode (whether the guest itself requested that, or whether we
requested it via the guest agent); that is, the new system_wakeup
monitor command needs to be something (in addition to mouse clicks,
serial console bytes, and timer expirations) that can cause a guest to
resume from S3.  Alas, virDomainResume has no flags argument, and I
don't know if we have any other API that would be good for the purpose.

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

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