[PATCH] ARM: KVM: Allow host virtual timer irq number to be different from guest virtual timer irq number

[Christoffer Dall]

On Apr 25, 2013, at 11:20 AM, Peter Maydell <peter.maydell at linaro.org> wrote:

> On 25 April 2013 19:04, Christoffer Dall <cdall at cs.columbia.edu> wrote:
>> I prefer not hard-coding this stuff in the kernel, but let user space
>> decide this. If we have good technical arguments not to do that (such
>> as knowing that this is always defined per-core and not for an SoC
>> (ARM guys?) then at least the patch should lookup the target processor
>> and set the irq number accordingly.
>
> Well, this is all implementation-defined. The ARM ARM mandates
> that the generic timers deliver a PPI, and that it must be the
> same PPI for all processors in an MP implementation, but not which
> PPI. The A15 and A7 happen to both be hardwired to ID27. You could
> in theory design a core which let the SoC configure the virtual
> timer ID (or let the guest arbitrarily program it, for that
> matter, I suppose), though I'm not sure why you'd want to.
>
> I think I'd take the simple approach of saying "the timer PPI
> is a fixed property of the guest CPU" unless somebody actually
> builds something where it isn't fixed... (for that CPU we
> could then define it as a feature argument to KVM_ARM_VCPU_INIT).
>

Ok, let's not bother with user space injection then, but instead of
hard defaulting to two specific cores, please make a switch statement
on the target CPU and log an error on init if it's an unknown core.