[libvirt] [PATCH] qemu: check for active domain after agent interaction

[Martin Kletzander]

On Wed, Aug 20, 2014 at 03:35:08PM -0600, Eric Blake wrote:
>Commit b606bbb41 reminded me that any time we drop locks to run
>back-to-back guest interaction commands, we have to check that
>the guest didn't disappear in between the two commands.  A quick
>audit found a couple of spots that were missing this check.
>
>* src/qemu/qemu_driver.c (qemuDomainShutdownFlags)
>(qemuDomainSetVcpusFlags): Check that domain is still up.
>
>Signed-off-by: Eric Blake <eblake at redhat.com>
>---
>
>I found this by inspection, and did not try to actually reproduce
>if it would cause failures.  I think a failure could be easier
>to reproduce by temporarily sticking a strategic sleep() call just
>prior to the qemuDomainObjExtAgent() call, and during the time
>while libvirtd is sleeping, manually cause the guest to exit.  But
>we've definitely fixed issues like this before.
>
> src/qemu/qemu_driver.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
>diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>index 02088cc..4ae76e5 100644
>--- a/src/qemu/qemu_driver.c
>+++ b/src/qemu/qemu_driver.c
>@@ -1921,6 +1921,13 @@ static int qemuDomainShutdownFlags(virDomainPtr dom, unsigned int flags)
>         (ret < 0 && (acpiRequested || !flags))) {
>         qemuDomainSetFakeReboot(driver, vm, isReboot);
>
>+        /* Even if agent failed, we have to check if guest went away
>+         * by itself while our locks were down.  */
>+        if (useAgent && !virDomainObjIsActive(vm)) {
>+            ret = 0;
>+            goto endjob;
>+        }
>+

I'm thinking about a place where we could stick this to make it more
generic, but can't find one.  That would be a completely different
cleanup anyway, so ACK to this.

Martin

>         qemuDomainObjEnterMonitor(driver, vm);
>         ret = qemuMonitorSystemPowerdown(priv->mon);
>         qemuDomainObjExitMonitor(driver, vm);
>@@ -4360,6 +4367,12 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
>         if (ncpuinfo < 0)
>             goto endjob;
>
>+        if (!virDomainObjIsActive(vm)) {
>+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
>+                           _("domain is not running"));
>+            goto endjob;
>+        }
>+
>         if (qemuAgentUpdateCPUInfo(nvcpus, cpuinfo, ncpuinfo) < 0)
>             goto endjob;
>
>--
>1.9.3
>
>--
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