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


From: Fedorov Sergey
Subject: Re: [Qemu-devel] [RFC PATCH 05/21] target-arm: add CPU Monitor mode
Date: Wed, 04 Dec 2013 16:33:15 +0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1


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.


The motiviation is less VMSD version bumps in ARM CPU (a place where I
expect assume such version bumps to be considerable annoyance).
Well, they're only a problem at the point where we start trying
to support cross-version migration; we're not at that point yet...

thanks
-- PMM


Best regards,
Sergey Fedorov



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