Alexander Graf <[email protected]> writes:

> On 11.11.2013, at 15:02, Aneesh Kumar K.V <[email protected]> 
> wrote:
>
>> From: "Aneesh Kumar K.V" <[email protected]>
>> 
>> Don't try to compute these values.
>> 
>> Signed-off-by: Aneesh Kumar K.V <[email protected]>
>> ---
>> 
>> NOTE: I am not sure why we were originally computing dsisr and dar. So may be
>> we need a variant of this patch. But with this and the additional patch
>> "powerpc: book3s: PR: Enable Little Endian PR guest" I am able to get a 
>> Little Endian
>> PR guest to boot.
>
> It's quite easy to find out - git blame tells you all the history and points 
> you to commit ca7f4203b.
>
> commit ca7f4203b9b66e12d0d9968ff7dfe781f3a9695a
> Author: Alexander Graf <[email protected]>
> Date:   Wed Mar 24 21:48:28 2010 +0100
>
>     KVM: PPC: Implement alignment interrupt
>
>     Mac OS X has some applications - namely the Finder - that require 
> alignment
>     interrupts to work properly. So we need to implement them.
>
>     But the spec for 970 and 750 also looks different. While 750 requires the
>     DSISR and DAR fields to reflect some instruction bits (DSISR) and the 
> fault
>     address (DAR), the 970 declares this as an optional feature. So we need
>     to reconstruct DSISR and DAR manually.
>
>     Signed-off-by: Alexander Graf <[email protected]>
>     Signed-off-by: Avi Kivity <[email protected]>
>
> Read this as "on 970, alignment interrupts don't give us DSISR and DAR of the 
> faulting instruction" as otherwise I wouldn't have implemented it.
>
> So this is clearly a nack on this patch :).

I can possibly do a if (cpu_has_feature(CPU_FTR_ARCH_201)). But do we need
to do that ? According to Paul we should always find DAR.

-aneesh

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