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

[Jan Kiszka]

On 2012-01-27 21:48, Anthony Liguori wrote:
> 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<address@hidden>
>>
>> Cc: Avi Kivity<address@hidden>
>> Cc: Marcelo Tosatti<address@hidden>
>> Cc: Jan Kiszka<address@hidden>
>> Cc: address@hidden
>> Cc: address@hidden
>> Cc: address@hidden
>> ---
>> 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.

Yep, but needs to be redirected after the file renaming in upstream.

>  What's the state of the kernel
> bits?  I would expect this through uq/master.

Kernel bits aren't merged yet. And the kernel headers will have to be
updated in a previous step.

BTW, this series [1] would be nice to have. Dunno if there is a pull
planned, but anyone trying to extend the KVM interface current runs
against this.

Jan

[1] http://thread.gmane.org/gmane.comp.emulators.qemu/132962

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