Re: [Xen-devel] [PATCH 00/10] x86/hvm: pkeys, add memory protection-key support

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of Jan Beulich
> Sent: Tuesday, November 17, 2015 6:26 PM
> To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Tian, Kevin <kevin.tian@xxxxxxxxx>; wei.liu2@xxxxxxxxxx;
> ian.campbell@xxxxxxxxxx; stefano.stabellini@xxxxxxxxxxxxx;
> george.dunlap@xxxxxxxxxxxxx; ian.jackson@xxxxxxxxxxxxx; xen-
> devel@xxxxxxxxxxxxx; Nakajima, Jun <jun.nakajima@xxxxxxxxx>; Han,
> Huaitong <huaitong.han@xxxxxxxxx>; keir@xxxxxxx
> Subject: Re: [Xen-devel] [PATCH 00/10] x86/hvm: pkeys, add memory
> protection-key support
> 
> >>> On 16.11.15 at 18:45, <andrew.cooper3@xxxxxxxxxx> wrote:
> > Furthermore, it is unclear (given the unwritten ABI) whether it is even
> > safe to move _PAGE_GNTTAB out of the way, as this is visible to a PV guest.
> 
> It seems pretty clear to me that this would be unsafe: It being
> part of L1_DISALLOW_MASK, if it moved and a guest used the
> bit for its own purposes, the guest would break. I guess we'll
> need an ELF note by which the guest can advertise which of the
> available bits it doesn't care about itself.

Actually, we don't expose this feature to PV guest, we only expose it
to HVM. In that case, is there still issues like you discussed above?

Thanks,
Feng

> 
> Jan
> 
> 
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