[PATCH 4/6] KVM: PPC: Book3E: Add AltiVec support

[Alexander Graf]

On 03.07.2013, at 20:36, Scott Wood wrote:

> On 07/03/2013 12:07:30 PM, Alexander Graf wrote:
>> On 03.07.2013, at 18:49, Caraman Mihai Claudiu-B02008 wrote:
>> >>>> Do we need to do this even when the guest doesn't use Altivec? Can't
>> >> we
>> >>>> just load it on demand then once we fault? This code path really
>> >> should
>> >>>> only be a prefetch enable when MSR_VEC is already set in guest
>> >> context.
>> >>>
>> >>> No we can't, read 6/6.
>> >>
>> >> So we have to make sure we're completely unlazy when it comes to a KVM
>> >> guest. Are we?
>> >
>> > Yes, because MSR[SPV] is under its control.
>> Oh, sure, KVM wants it unlazy. That part is obvious. But does the kernel always give us unlazyness? The way I read the code, process.c goes lazy when !CONFIG_SMP.
>> So the big question is why we're manually enforcing FPU giveup, but not Altivec giveup? One of the 2 probably is wrong :).
> 
> Why do you think we're not enforcing it for Altivec?  Is there some specific piece of code you're referring to that is different in this regard?

Well, apparently because I misread the code :). All is well.


Alex