[PATCH] arm64: KVM: Support X-Gene guest VCPU on APM X-Gene host

[Peter Maydell]

On 15 July 2013 15:21, Alexander Graf <agraf at suse.de> wrote:
> On 15.07.2013, at 16:04, Anup Patel wrote:
>> On Mon, Jul 15, 2013 at 6:32 PM, Alexander Graf <agraf at suse.de> wrote:
>>> Anything that is compatible is compatible :). I don't know
>>> the product roadmaps for X-Gene cores, but you will want to
>>> make the field here as coarse grained as possible, while
>>> maintaining the guarantee that a guest still behaves the same.
>>
>> Actually, I don't see X-Gene cores changing in-terms of register
>> interface available to EL1 and EL0 in near future. This is the
>> reason why I had named the target as KVM_ARM_TARGET_XGENE_V8.
>
> So where does the v8 come from? Is there any non-ARMv8 XGene? If
> not, this is v1 really, right? What if we just call it v1 instead?
> Then when a new core comes up that needs different treatment, we
> create a new target.

I think what we're actually seeing here is that we started with
a design that specifically said (in the v7 space) "only A15
on A15", and we're now trying to broaden that out, only we
haven't actually set out anywhere how that broadening is
supposed to work (ie what range of hosts will work with
what range of guests, and how, and whether we want to have
a "give me a guest CPU that looks like the host CPU" option).

I think the original idea was that userspace would say
which CPU it wanted, and the kernel would know about that
CPU (including details like ID and feature registers which
are going to vary from core to core).

thanks
-- PMM