Re: [Qemu-devel] [PATCH v2 1/2] KVM_CAP_IRQFD and KVM_CAP_IRQFD_RESAMPLE checks

[Eric Auger]

On 09/03/2014 02:50 PM, Christian Borntraeger wrote:
> On 03/09/14 11:54, Eric Auger wrote:
> [...]
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
> [...]
>> @@ -1548,6 +1549,12 @@ int kvm_init(MachineClass *mc)
>>      kvm_eventfds_allowed =
>>          (kvm_check_extension(s, KVM_CAP_IOEVENTFD) > 0);
>>
>> +    kvm_irqfds_allowed =
>> +        (kvm_check_extension(s, KVM_CAP_IRQFD) > 0);
>                                    ^^^^^^^^^^^^^
>> +
>> +    kvm_resamplefds_allowed =
>> +        (kvm_check_extension(s, KVM_CAP_IRQFD_RESAMPLE) > 0);
>> +
> [...]
> 
>> diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
>> index a85a480..f937568 100644
>> --- a/target-s390x/kvm.c
>> +++ b/target-s390x/kvm.c
>> @@ -1290,7 +1290,6 @@ void kvm_arch_init_irq_routing(KVMState *s)
>>       * have to override the common code kvm_halt_in_kernel_allowed setting.
>>       */
>>      if (kvm_check_extension(s, KVM_CAP_IRQ_ROUTING)) {
>                                   ^^^^^^^^^^^^^^^^^^^
>> -        kvm_irqfds_allowed = true;
>>          kvm_gsi_routing_allowed = true;
>>          kvm_halt_in_kernel_allowed = false;
>>      }
> 
> 
> 
> I first thought that this is wrong, because on s390 we forgot to announce 
> IRQFD when we introduced
> it. As you can see in both hunks, we check for KVM_CAP_IRQ_ROUTING and not 
> for CAP_IRQFD
> 
> Luckily, the kernel got fixed with commit 
> ebc3226202d5956a5963185222982d435378b899
> ("KVM: s390: announce irqfd capability") and the capability was introduced 
> with 
> commit 84223598778ba08041f4297fda485df83414d57e ("KVM: s390: irq routing for 
> adapter interrupts").
> Looks that both patches first appear with 3.15, so there should be no kernel 
> version that
> is affected by this change. You might want to add that to your changelog to 
> help distros that
> 84223598778ba08041f4297fda485df83414d57e also needs 
> ebc3226202d5956a5963185222982d435378b899.
Hi Christian,

I will add this information to the changelog. I effectively checked the
cap was advertised in s390 arch but I was not aware of the history.

Thanks

Best Regards

Eric
> 
> 
> 
> Christian
>