[PATCH] powerpc: book3s: kvm: Use the saved dsisr and dar values

[Alexander Graf]

> Am 19.12.2013 um 08:02 schrieb "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com>:
> 
> Alexander Graf <agraf at suse.de> writes:
> 
>>> On 11.11.2013, at 15:02, Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com> wrote:
>>> 
>>> From: "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com>
>>> 
>>> Don't try to compute these values.
>>> 
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>>> ---
>>> 
>>> 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 <agraf at suse.de>
>> 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 <agraf at suse.de>
>>    Signed-off-by: Avi Kivity <avi at redhat.com>
>> 
>> 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.

Paul only mentioned DAR, not DSISR. Please verify whether 970 gives us a proper DAR value - we can then remove that part.

But for DSISR I'm not convinced CPUs above 970 handle this correctly. So we would at least need a guest cpu check to find out whether the vcpu expects a working dsisr and emulate it then.

I don't really fully understand the problem though. Why does the calculation break at all for you?


Alex