Re: [RFC 0/6] KVM: arm/arm64: gsi routing support

[Eric Auger <eric.auger@linaro.org>]

Hi Pavel,
On 06/24/2015 02:20 PM, Pavel Fedin wrote:
>  Hello!
> 
>> What I can simply do is preventing any non identity mapping for irqchip
>> routing entries, ie. gsi != irqchip.pin. This fixes the problem of
>> KVM_IRQ_LINE. This check can happen in arm kvm_set_routing_entry() and
>> that's it.
> 
>  You cannot fix problem of KVM_IRQ_LINE because anyway with this ioctl on ARM you should OR your
> value with (1 << 24), so this is actually not plain GSI any more.
>  KVM_IRQ_LINE is never used for triggering MSIs, so i think the easiest thing to do is to just leave
> it doing what it does.

Yes I agree with you. in my next version I simply aknowledge the fact
GSI_ROUTING does not apply to KVM_IRQ_LINE on arm/arm64 but only applies
to KVM_IRQFD.
> 
>  As to irqchip routing of irqfd's, why not? By default all GSIs would be SPIs, then this can be
> changed by userspace, or reverted back... Who cares? When using direct mapping qemu never calls
> routing functions, so it's OK.

Indeed either we leave fully open irqchip routing saying that
irqchip.pin corresponds to an SPI ID. But personally I would prefer we
check irqchip routing entries have flat mapping, ie gsi = irqchip.pin
since in any case we don't want/expect the userspace to play with that.

Best Regards

Eric
> 
> 
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
> 
>