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

[Peter Crosthwaite]

On Wed, Dec 4, 2013 at 10:35 PM, Peter Maydell <address@hidden> wrote:
> 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.
>

+1. Patch is good for the moment.

> thanks
> -- PMM
>