Re: [Qemu-devel] [PATCH V7] Guest stop notification

[Anthony Liguori <aliguori@us.ibm.com>]

On 01/17/2012 12:27 PM, Eric B Munson wrote:
> Often when a guest is stopped from the qemu console, it will report spurious
> soft lockup warnings on resume.  There are kernel patches being discussed that
> will give the host the ability to tell the guest that it is being stopped and
> should ignore the soft lockup warning that generates.  This patch uses the qemu
> Notifier system to tell the guest it is about to be stopped.
>
> Signed-off-by: Eric B Munson<emunson@mgebm.net>
>
> Cc: Avi Kivity<avi@redhat.com>
> Cc: Marcelo Tosatti<mtosatti@redhat.com>
> Cc: Jan Kiszka<jan.kiszka@siemens.com>
> Cc: ryanh@linux.vnet.ibm.com
> Cc: aliguori@us.ibm.com
> Cc: kvm@vger.kernel.org
> ---
> Changes from V6:
>   Remove unnecessary include
>
> Changes from V5:
>   KVM_GUEST_PAUSED is now a per vm ioctl instead of per vcpu
>
> Changes from V4:
>   Test if the guest paused capability is available before use
>
> Changes from V3:
>   Collapse new state change notification function into existsing function.
>   Correct whitespace issues
>   Change ioctl name to KVMCLOCK_GUEST_PAUSED
>   Use for loop to iterate vpcu's
>
> Changes from V2:
>   Move ioctl into hw/kvmclock.c so as other arches can use it as it is
> implemented
>
> Changes from V1:
>   Remove unnecessary encapsulating function
>
>   hw/kvmclock.c |   11 +++++++++++
>   1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/hw/kvmclock.c b/hw/kvmclock.c
> index 3b9fb20..ad79f52 100644
> --- a/hw/kvmclock.c
> +++ b/hw/kvmclock.c
> @@ -64,10 +64,21 @@ static int kvmclock_post_load(void *opaque, int version_id)
>   static void kvmclock_vm_state_change(void *opaque, int running,
>                                        RunState state)
>   {
> +    int ret;
>       KVMClockState *s = opaque;
> +    int cap_guest_paused = kvm_check_extension(kvm_state, KVM_CAP_GUEST_PAUSED);
>
>       if (running) {
>           s->clock_valid = false;
> +
> +        if (!cap_guest_paused) {
> +            return;
> +        }
> +
> +        ret = kvm_vm_ioctl(kvm_state, KVMCLOCK_GUEST_PAUSED, 0);
> +        if (ret) {
> +            fprintf(stderr, "kvmclock_vm_state_change: %s\n", strerror(-ret));
> +        }
>       }
>   }


This change looks harmless enough.  What's the state of the kernel bits?  I 
would expect this through uq/master.

Regards,

Anthony Liguori

>