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Re: [libvirt] [PATCH 3/3] qemu: Stop guest CPUs before creating a snapshot



On Fri, Feb 25, 2011 at 07:04:11PM +0100, Jiri Denemark wrote:
> ---
>  src/qemu/qemu_driver.c |   37 ++++++++++++++++++++++++++++++++-----
>  1 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index ba046d7..a02d1b9 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -6041,21 +6041,47 @@ cleanup:
>  
>  /* The domain is expected to be locked and active. */
>  static int
> -qemuDomainSnapshotCreateActive(struct qemud_driver *driver,
> +qemuDomainSnapshotCreateActive(virConnectPtr conn,
> +                               struct qemud_driver *driver,
>                                 virDomainObjPtr *vmptr,
>                                 virDomainSnapshotObjPtr snap)
>  {
>      virDomainObjPtr vm = *vmptr;
>      qemuDomainObjPrivatePtr priv = vm->privateData;
> -    int ret;
> +    bool resume = false;
> +    int ret = -1;
>  
>      if (qemuDomainObjBeginJobWithDriver(driver, vm) < 0)
>          return -1;
>  
> +    if (vm->state == VIR_DOMAIN_RUNNING) {
> +        /* savevm monitor command pauses the domain emitting an event which
> +         * confuses libvirt since it's not notified when qemu resumes the
> +         * domain. Thus we stop and start CPUs ourselves.
> +         */

Not having a resume event from QEMU sounds like a QEMU bug, right ?

> +        if (qemuProcessStopCPUs(driver, vm) < 0)
> +            goto cleanup;
> +
> +        resume = true;
> +        if (!virDomainObjIsActive(vm)) {
> +            qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                            _("guest unexpectedly quit"));
> +            goto cleanup;
> +        }
> +    }
> +
>      qemuDomainObjEnterMonitorWithDriver(driver, vm);
>      ret = qemuMonitorCreateSnapshot(priv->mon, snap->def->name);
>      qemuDomainObjExitMonitorWithDriver(driver, vm);
>  
> +cleanup:
> +    if (resume && virDomainObjIsActive(vm) &&
> +        qemuProcessStartCPUs(driver, vm, conn) < 0 &&
> +        virGetLastError() == NULL) {
> +        qemuReportError(VIR_ERR_OPERATION_FAILED, "%s",
> +                        _("resuming after snapshot failed"));
> +    }
> +
>      if (qemuDomainObjEndJob(vm) == 0)
>          *vmptr = NULL;
>  
> @@ -6100,18 +6126,19 @@ static virDomainSnapshotPtr qemuDomainSnapshotCreateXML(virDomainPtr domain,
>      if (!(snap = virDomainSnapshotAssignDef(&vm->snapshots, def)))
>          goto cleanup;
>  
> +    snap->def->state = vm->state;
> +
>      /* actually do the snapshot */
>      if (!virDomainObjIsActive(vm)) {
>          if (qemuDomainSnapshotCreateInactive(vm, snap) < 0)
>              goto cleanup;
>      }
>      else {
> -        if (qemuDomainSnapshotCreateActive(driver, &vm, snap) < 0)
> +        if (qemuDomainSnapshotCreateActive(domain->conn, driver,
> +                                           &vm, snap) < 0)
>              goto cleanup;
>      }
>  
> -    snap->def->state = vm->state;
> -
>      /* FIXME: if we fail after this point, there's not a whole lot we can
>       * do; we've successfully taken the snapshot, and we are now running
>       * on it, so we have to go forward the best we can

ACK

Daniel
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