Re: [PATCH RFC v2 6/6] KVM: introduce a new API for getting dirty

On 04/23/2010 03:59 PM, Alexander Graf wrote:
>
>> Ah so the 31st bit is optional as far as userspace is concerned?  What does it mean? (just curious)
>>      
> The 0x80000000 bit declares that a pointer is in 24-bit mode, so that applications can use the spare upper bits for random data.
>
> See http://en.wikipedia.org/wiki/31-bit for an explanation.
>    

Interesting.  Luckily AMD made the top 16 bits of pointers reserved in 
x86-64.

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