Re: VPMU backports for 4.6

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 01/20/2016 12:13 PM, Jan Beulich wrote:
>>>> On 20.01.16 at 17:12, <boris.ostrovsky@oracle.com> 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