[Libvir] big-endian support for libvirt - introduce GUEST_HANDLE infrastructure ?

[Richard W.M. Jones]

Christian Ehrhardt wrote:
>               Now look at the padding in e.g. 
> xen_v2s3_getdomaininfolistop: it
>        doesn't work on big-endian systems. This problem is why the
>        GUEST_HANDLE infrastructure is present in Xen. To work on
>        big-endian systems, libvirt will need this or a similar mechanism.

Understood.

> --- Current Questions ---
> We could now add several ugly ifdefs to libvirt code to differentiate 
> powerpc from the others and solve the issue described above, but I think 
> thats not a good solution.
> The GUEST_HANDLE mechanism would provide an architecture abstraction and 
> is already implemented/working in libxc.
> The question is, shouldn't libvirt actually use the GUEST_HANDLE 
> mechanism like libxc does (at least for the _v2d5_ structures) or are 
> there big arguments against it?
> I would create a patch to add the GUEST_HANDLE stuff in libvirt if there 
> is nothing against it, but I will need some help to test  it on 
> x86/x86_64/ia64 since I have no such machines here.
> If there is a major reason against the GUEST_HANDLE code, are there 
> other suggestions/preferences how to solve this?

I had a look at the GUEST_HANDLE code in libxc (specifically 
arch-powerpc.h vs arch-x86_{32,64}.h) and it looks as if something like 
this should go into libvirt.  I would just be careful about copying the 
code verbatim because libvirt & libxc are under slightly different licenses.

As for testing: we have no 64 bit PPC machines at all available for us 
to use that I'm aware of.  We have plenty of i386 & x86-64, and one or 
two IA64 machines.

Thanks for your analysis.

Rich.

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