Am 28.04.2015 um 13:37 schrieb Paolo Bonzini:
>> --- a/arch/powerpc/kvm/book3s_pr.c
>> +++ b/arch/powerpc/kvm/book3s_pr.c
>> @@ -891,7 +891,9 @@ int kvmppc_handle_exit_pr(struct kvm_run *run, struct
>> kvm_vcpu *vcpu,
>>
>> /* We get here with MSR.EE=1 */
>>
>> + local_irq_disable();
>> trace_kvm_exit(exit_nr, vcpu);
>> + local_irq_enable();
>> kvm_guest_exit();
>
> This looks wrong.
>
Yes it is.
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -773,11 +773,7 @@ static inline void kvm_guest_enter(void)
>>
>> static inline void kvm_guest_exit(void)
>> {
>> - unsigned long flags;
>> -
>> - local_irq_save(flags);
>
> Why no WARN_ON here?
Yes,WARN_ON makes sense.
Hmm, on the other hand the irqs_disabled call might be somewhat expensive again
(would boil down on s390 to call stnsm (store and and system mask) once for
query and once for setting.
so...
>
> I think the patches are sensible, especially since you can add warnings.
> This kind of code definitely knows if it has interrupts disabled or enabled
>
> Alternatively, the irq-disabled versions could be called
> __kvm_guest_{enter,exit}. Then you can use those directly when it makes
> sense.
..having a special __kvm_guest_{enter,exit} without the WARN_ON might be even
the cheapest way. In that way I could leave everything besides s390 alone and
arch maintainers can do a followup patch if appropriate.
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