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

Avi Kivity
2010-04-23T13:20:36Z

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.