Re: [patch 4/4] KVM: switch irq injection/acking to irq_lock

Avi Kivity
2009-05-24T14:53:14Z

Gregory Haskins wrote:
> Marcelo Tosatti wrote:
>
>> Switch irq injection/acking to irq_lock, and change PIO/MMIO paths
>> so that the device search is protected by kvm->lock, but not the
>> read/write callbacks (which is responsability of the device).
>>
>> Fix for http://article.gmane.org/gmane.comp.emulators.kvm.devel/32286.
>>
>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>
>> Index: kvm/arch/x86/kvm/i8254.c
>> ===================================================================
>> --- kvm.orig/arch/x86/kvm/i8254.c
>> +++ kvm/arch/x86/kvm/i8254.c
>> @@ -634,10 +634,10 @@ static void __inject_pit_timer_intr(stru
>> struct kvm_vcpu *vcpu;
>> int i;
>>
>> - mutex_lock(&kvm->lock);
>> + mutex_lock(&kvm->irq_lock);
>>
>>
>
> There would be advantages to having irq_lock be
> interrupt/nonpreempt-friendly design, such as s/mutex/spinlock. For
> instance, irqfd could inject the interrupt directly without deferring to
> a workqueue. I'm not sure if this is possible/easy, but its something
> to consider.
>

I agree, but let's make the first step splitting the interrupt and a
second step changing it to a spinlock. It's scary enough as is.

--
error compiling committee.c: too many arguments to function