[Qemu-devel] Re: [PATCH 2/3] Assume PPC64 host on PPC32 KVM

[Alexander Graf]

On 24.07.2009, at 15:15, Jan Kiszka wrote:

> Alexander Graf wrote:
> > On 24.07.2009, at 14:57, Jan Kiszka wrote:
> >
> > > Alexander Graf wrote:
> > > > On 24.07.2009, at 13:51, Jan Kiszka wrote:
> >
> > [...]
> >
> > > > There are no 32-bit PowerPC KVM kernels that can do dirty logging.
> > >
> > > By design or by lack of implementation?
> >
> > Lack of implementation.
> >
> > > And what if some other arch with support for both pops up? #ifdef
> > > HOST_PPC is no long-term solutions. And I see no need to install a
> > > temporary workaround given the currently existing kernel support.
> >
> > I'd like to have the qemu bits sorted out while polishing the kvm  
> > parts,
> > so when kvm support shows up mainline there's a working userspace  
> > part.
>
> I understand. But the risk is that what you submit to qemu and kvm may
> receive different reviews and finally look different. So for stuff  
> which
> concerns not yet existing (or fully implemented) interfaces, the other
> way around is better. Specifically if there is a "risk" that it makes
> into a qemu release before the corresponding kernel bits are official.

Well, it looks like doing the qemu parts first was a good idea,  
because we can still change the interfaces :-).

> > > > > In any case, I suggest to pin down the word size and use it for  
> > > > > all
> > > > > hosts.
> > > >
> > > > That would break backwards compatibility.
> > >
> > > x86 and ia64 are little endian for which is doesn't matter,  
> > > PowerPC and
> > > s390 don't support dirty logging so far. Or what would break?
> >
> > Oh you mean just always use u32* and be done with it?
>
> Or u64* as you suggested. It doesn't matter for existing support, and
> future support should simply use that type even on 32-bit hosts.

Right. I guess it's time for v2!

Alex