On Tue, Dec 30, 2008 at 12:08:01PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> Certain clocks (such as TSC) in older 2.6 guests overaccount for lost
>> ticks, causing severe time drift. Interrupt reinjection magnifies the
>> problem.
>>
>> Provide an option to disable it.
>>
>> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>
>>
>> Index: kvm/arch/x86/kvm/i8254.c
>> ===================================================================
>> --- kvm.orig/arch/x86/kvm/i8254.c
>> +++ kvm/arch/x86/kvm/i8254.c
>> @@ -201,6 +201,9 @@ static int __pit_timer_fn(struct kvm_kpi
>> if (!atomic_inc_and_test(&pt->pending))
>> set_bit(KVM_REQ_PENDING_TIMER, &vcpu0->requests);
>> + if (pt->no_reinject)
>> + atomic_set(&pt->pending, 1);
>> +
>>
>
> What about moving this to the place where we atomic_inc()? Any reason
> not to?
The atomic_inc_and_test is right above, and we want to set
KVM_REQ_PENDING_TIMER on 0->1 transitions, so better keep it
separate. BTW the KVM_REQ_PENDING_TIMER optimization is broken
(atomic_inc_and_test returns true if the _new_ value is zero) but thats
another issue.
Can't see the improvement you're suggesting.
>> --- kvm.orig/arch/x86/kvm/i8254.h
>> +++ kvm/arch/x86/kvm/i8254.h
>> @@ -9,6 +9,7 @@ struct kvm_kpit_timer {
>> s64 period; /* unit: ns */
>> s64 scheduled;
>> atomic_t pending;
>> + bool no_reinject;
>> };
>>
>
> Negative logic = !good. Call it reinject and init to true.
Sure.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
