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

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

Hi Pavel,
On 06/23/2015 09:38 AM, Pavel Fedin wrote:
>  Hello!
> 
>> What is done currently at qemu level for other archs -  if I understand
>> it correctly -  is there is static GSI routing for standard IRQ.
> 
>  Yes, this is correct. GSI number = SPI number for ARM. Also something similar for MIPS (haven't
> study that).
> 
>> For MSI
>> irqfd setup they use spare gsi number not yet used for GSI routing < max
>> route number.
> 
>  No.
>  On ARM with vGICv2m MSI data is effectively IRQ offset, with base being 32. So, original convention
> works without any change, they simply retrieve SPI number from MSI data and set up irqfd to that
> SPI. No allocation is done. 
Yes on ARM we use gsi direct mapping feature. I was talking about what
is done without this "gsi direct mapping" feature. In that case the low
GSI numbers are used by irqchip routing entries. So kvm_irqchip_get_virq
returns a gsi beyond the irqchip routed gsi's.

Eric
>  Allocation is done only on x86, with routing. They just allocate GSI numbers starting from zero and
> route them to something (either irqchip or MSI).
> 
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
> 
>