Re: [Qemu-devel] Re: [PATCH v2] qemu-kvm: Speed up of the dirty-bitmap-traveling

[Alexander Graf]

Anthony Liguori wrote:
> On 02/10/2010 10:00 AM, Alexander Graf wrote:
>   
>> On PPC the bitmap is Little Endian.
>>   
>>     
>
> Out of curiousity, why? It seems like an odd interface.
>   

Because on PPC, you usually run PPC32 userspace code on a PPC64 kernel.
Unlike with x86, there's no real benefit in using 64 bit userspace.

So thanks to the nature of big endianness, that breaks our set_bit
helpers, because they assume you're using "long" data types for the
bits. While that's no real issue on little endian, since the next int is
just the high part of a u64, it messes everything up on ppc.

For more details, please just look in the archives on my patches to make
it little endian.


Alex