Re: [Qemu-devel] [RFC PATCH 05/21] target-arm: add CPU Monitor mode

[Peter Maydell]

On 4 December 2013 12:33, Fedorov Sergey <address@hidden> wrote:
>
> On 12/04/2013 03:18 PM, Peter Maydell wrote:
>>
>> On 4 December 2013 10:58, Peter Crosthwaite
>> <address@hidden> wrote:
>>>
>>> So what im proposing is just a slightly more general patch. Is it
>>> really any more complicated than just applying your change pattern for
>>> the hyp mode?
>>
>> I think it would be, because of the wrinkle that hyp mode doesn't
>> have a banked LR, so the existing "assume we can just translate
>> the mode into a single index good for both LR and SP" logic
>> would break.
>>
>> The minimal change if we wanted to keep VMSD bumps to a
>> minimum would be to increase the size of the banked_spsr[]
>> and banked_r13[] arrays to allow for Hyp mode but do nothing
>> else (except add a comment about it I guess).
>
>
> If we want to bump VMSD just once for monitor + hypervisor mode then we need
> to add ELR_hyp register definition too. I think then it would be better to
> implement hypervisor mode and its special banking scheme, too. But I doubt
> it worth to combine these two things into one patch.

It's possible to add single new fields to the VMState without
requiring a compatibility break, by marking the new field as
"only present in version X or greater"; new elements on the
end of arrays are a little fiddlier.

But yes, I think we should just not worry about possible future
Hyp mode now. Let's stick with your current patch.

thanks
-- PMM