Re: [RFC 5/5] KVM: ARM: Access all registers via KVM_GET_ONE_REG/KVM_SET_ONE_REG.

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On Sep 1, 2012, at 6:25 AM, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote:

> On 1 September 2012 10:16, Avi Kivity <avi@xxxxxxxxxx> wrote:
>> On 08/29/2012 11:21 AM, Rusty Russell wrote:
>>>>> +       /* Coprocessor 0 means we want a core register. */
>>>>> +       if ((u32)reg->id >> KVM_REG_ARM_COPROC_START == 0)
>>>>> +               return set_core_reg(vcpu, reg);
>>>> 
>>>> ...but if we do go this path, you can't use coprocessor 0
>>>> to mean core register -- cp0 could be a valid coprocessor
>>>> (the ARM ARM reserves cp0..cp7 for "vendor specific features").
>>>> Use something outside 0..15.
>>> 
>>> OK, changed that too (16).
> 
>> And tomorrow they will add 16.
> 
> Not possible in the instruction encoding :-) We haven't used
> anywhere near all the coprocessors (even given we've let the
> vendors have 0..7, ARM itself uses only 10 and 11 for the FPU,
> 14 for debug/perf and 15 for system control (and 14 and 15 still
> have lots of spare space).
> 

Yeah, but folding core registers under coprocessors feels just too fishy, so I think we should have a separate field. 

-Christoffer--
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