Re: [PATCH 2/8 v2] Maintain back mapping from irqchip/pin to gsi.

[Gleb Natapov <gleb@redhat.com>]

On Wed, Aug 12, 2009 at 11:09:58AM +0300, Avi Kivity wrote:
> On 08/11/2009 03:31 PM, Gleb Natapov wrote:
>> Maintain back mapping from irqchip/pin to gsi to speedup
>> interrupt acknowledgment notifications.
>>
>> Signed-off-by: Gleb Natapov<gleb@redhat.com>
>> ---
>>   include/linux/kvm_host.h |    1 +
>>   virt/kvm/irq_comm.c      |   24 +++++++++++-------------
>>   2 files changed, 12 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index 09df31d..d2b8eb3 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -133,6 +133,7 @@ struct kvm_kernel_irq_routing_entry {
>>   };
>>
>>   struct kvm_irq_routing_table {
>> +	int chip[3][KVM_IOAPIC_NUM_PINS];
>>    
>
> KVM_NR_IRQCHIPS
>
> An alternative implementation is to embed a lookup table in each  
> irqchip.  I don't think it's really necessary.
>
>> --- a/virt/kvm/irq_comm.c
>> +++ b/virt/kvm/irq_comm.c
>> @@ -168,21 +168,13 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
>>   {
>>   	struct kvm_irq_ack_notifier *kian;
>>   	struct hlist_node *n;
>> -	unsigned gsi = pin;
>> -	int i;
>> +	unsigned gsi;
>>
>>   	trace_kvm_ack_irq(irqchip, pin);
>>
>> -	for (i = 0; i<  kvm->irq_routing->nr_rt_entries; i++) {
>> -		struct kvm_kernel_irq_routing_entry *e;
>> -		e =&kvm->irq_routing->rt_entries[i];
>> -		if (e->type == KVM_IRQ_ROUTING_IRQCHIP&&
>> -		    e->irqchip.irqchip == irqchip&&
>> -		    e->irqchip.pin == pin) {
>> -			gsi = e->gsi;
>> -			break;
>> -		}
>> -	}
>> +	gsi = kvm->irq_routing->chip[irqchip][pin];
>> +	if (gsi == -1)
>> +		gsi = pin;
>>    
>
> What's this?
>
If there is not GSI mapping use pin as gsi. This what current code does.
We can BUG() here I think.

--
			Gleb.