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Re: [Qemu-devel] [PATCH] target-arm: Added CP15 VBAR support

From: Peter Crosthwaite
Subject: Re: [Qemu-devel] [PATCH] target-arm: Added CP15 VBAR support
Date: Wed, 26 Jun 2013 11:57:49 +1000

Hi Peter,

(Sorry about the delay),

On Wed, Feb 27, 2013 at 8:10 PM, Peter Maydell <address@hidden> wrote:
> On 27 February 2013 07:16, Peter Crosthwaite
> <address@hidden> wrote:
>> From: Nathan Rossi <address@hidden>
>> Added Vector Base Address remapping on ARM v7.
> This one's tricky because the VBAR only exists in CPUs with
> TrustZone, and strictly speaking QEMU models a non-TrustZone
> core. However we already have some dummy cp15 registers which
> are really TZ-only just to get guests working, and this may
> well fall into that category.
> I need to have a think about how we can coherently define
> what QEMU does about TZ so we can have a better idea of
> what should and shouldn't be implemented. (If you have any
> suggestions I'm open to them.)


> On the patch itself:
>  * you've forgotten to bump the cpu vmstate version
>  * I'm trying to move towards using the official register
>    abbreviations in cpu struct member names
>  * the low bits of VBAR are "UNK/SBZP", which means our
>    implementation must ignore writes and read as zeroes. So
>    you need to do the masking in the write-accessor, not at
>    point of use


>  * we can just rely on the fact that the vbar field will be
>    zero when QEMU is emulating a pre-v7 core, so you can
>    avoid the feature check on use



> thanks
> -- PMM

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