Re: [PATCH 27/27] KVM: PPC: Add Documentation about PV interface

Benjamin Herrenschmidt
2010-07-03T22:42:36Z

On Fri, 2010-07-02 at 20:41 +0200, Alexander Graf wrote:
> The u64s are 64-bit aligned, should they always be?
>
> That's obvious, isn't it? And the ABI only specifies u64s to be 32 bit
> aligned, no? At least that's what ld and std specify.

No, the PowerPC ABI specifies u64's to be 64-bit aligned, even for
32-bit binaries.

Ben.

> >
> >> +The "ld" and "std" instructions are transormed to "lwz" and "stw"
> instructions
> >> +respectively on 32 bit systems with an added offset of 4 to
> accomodate for big
> >> +endianness.
> >
> > Will this add never overflow? Is there anything that checks for it?
>
> It basically means that to access dar, we either do
>
> ld rX, DAR(0)
>
> or
>
> lwz rX, DAR+4(0)
>
>
> >
> >> +mtmsrd rX, 0 b <special mtmsr section>
> >> +mtmsr b <special mtmsr section>
> >
> > mtmsr rX
>
> Nod.