Re: [GIT PULL] Add KVM support for Book3s_64 (PPC64) hosts v3

[Avi Kivity <avi@redhat.com>]

On 07/26/2009 08:25 PM, Alexander Graf wrote:
>>>
>>>>> Perhaps we can get away with disabling 32-on-64 for the 
>>>>> configurations that break to start with.
>>>>
>>>> 32-on-64 only breaks for big endian which nobody except for this 
>>>> target implements. Since my PPC enabling patches for qemu change 
>>>> the type to uint64_t always, nobody is broken right now.
>>>>
>>>
>>> That assumes you implement set_bit_u64(), no?
>>
>> No, little endian works as-is :-).
>
>
> Let me rephrase: It shouldn't if I understand little endian correctly :).
>
> I haven't actually verified that 32 on 64 doesn't break. But then 
> again that's a rather uncommon configuration for x86 anyways, but 
> really common on ppc.

I meant disable 32-on-64 ppc.  32-on-64 x86 is supported and works 
(though it is rare).

Given that you say 32-on-64 ppc is common, it could only be a short term 
fix until we implemlement u64 bitops.  Alternatively we can mangle the 
bitmap when copying it to userspace.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.