[PATCH V4] POWERPC: BOOK3S: KVM: Use the saved dar value and generic make_dsisr

[Alexander Graf]

> Am 05.05.2014 um 16:57 schrieb Olof Johansson <olofj at google.com>:
> 
> [Now without HTML email -- it's what you get for cc:ing me at work
> instead of my upstream email :)]
> 
> 2014-05-05 7:43 GMT-07:00 Alexander Graf <agraf at suse.de>:
>> 
>>> On 05/05/2014 04:26 PM, Aneesh Kumar K.V wrote:
>>> 
>>> Alexander Graf <agraf at suse.de> writes:
>>> 
>>>>> On 05/04/2014 07:21 PM, Aneesh Kumar K.V wrote:
>>>>> 
>>>>> Although it's optional IBM POWER cpus always had DAR value set on
>>>>> alignment interrupt. So don't try to compute these values.
>>>>> 
>>>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>>>>> ---
>>>>> Changes from V3:
>>>>> * Use make_dsisr instead of checking feature flag to decide whether to use
>>>>>    saved dsisr or not
>>> ....
>>> 
>>>>>   ulong kvmppc_alignment_dar(struct kvm_vcpu *vcpu, unsigned int inst)
>>>>>   {
>>>>> +#ifdef CONFIG_PPC_BOOK3S_64
>>>>> +       return vcpu->arch.fault_dar;
>>>> 
>>>> How about PA6T and G5s?
>>> Paul mentioned that BOOK3S always had DAR value set on alignment
>>> interrupt. And the patch is to enable/collect correct DAR value when
>>> running with Little Endian PR guest. Now to limit the impact and to
>>> enable Little Endian PR guest, I ended up doing the conditional code
>>> only for book3s 64 for which we know for sure that we set DAR value.
>> 
>> 
>> Yes, and I'm asking whether we know that this statement holds true for PA6T and G5 chips which I wouldn't consider IBM POWER. Since the G5 is at least developed by IBM, I'd assume its semantics here are similar to POWER4, but for PA6T I wouldn't be so sure.
> 
> Thanks for looking out for us, obviously IBM doesn't (based on the
> reply a minute ago).
> 
> In the end, since there's been no work to enable KVM on PA6T, I'm not
> too worried. I guess it's one more thing to sort out (and check for)
> whenever someone does that.
> 
> I definitely don't have cycles to deal with that myself at this time.
> I can help find hardware for someone who wants to, but even then I'm
> guessing the interest is pretty limited.

I know of at least 1 person who successfully runs PR KVM on a PA6T, so it's neither neglected nor non-working.

If you can get me access to a pa6t system I can easily check whether alignment interrupts generate dar and dsisr properly :).


Alex