Re: [Xen-devel] VPMU backports for 4.6

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/20/2016 12:13 PM, Jan Beulich wrote:
> > > > On 20.01.16 at 17:12, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > There two patches need to be backported to 4.6
> >
> > fb424bf x86/VPMU: don't allow any non-zero writes to MSR_IA32_PEBS_ENABLE
> > 31af0d7 x86/VPMU: check more carefully which bits are allowed to be
> > written to MSRs
> "Need to be" is pretty strong for an unsupported subsystem. In fact
> I had already considered those and then decided not to take them.
> So with you asking for them I'm not really sure what to do...
"Need to" may indeed have been a bit too much.

Since there is a potential for crashing the hypervisor I think we should 
have those two in 4.6, even if we don't officially support VPMU.
(As a side --- XSA-163 says that VPMU is "unsupported security-wise". Do 
we make any distinction between a feature being generally or 
security-wise unsupported?)
-boris

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