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Re: [Xen-devel] [V2 PATCH 0/9] x86/hvm: pkeys, add memory protection-key support

On Fri, 2015-11-27 at 12:59 +0000, Andrew Cooper wrote:
> Just for my own understand, do you have a sample use-case for
> protection
> keys?
> As everything can WRPKRU, I cant see how it would actually be useful.
> Clearly there is a usecase or you (Intel) wouldn't have gone to the
> effort of putting into silicon.
> ~Andrew

I understand PKU is a active memory protection, pkru register is thread
-private, every thread can only change its pkru value, it is a
enhancement of pte write/access, it provides two advantage:
1.During permission changes, we only need update pkru register instead 
  of pte, so it can reduce the need to perform TLB shootdowns.
2.Compared with traditional read and write permissions, it can provide
thread-private permissions.

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