Re: [PATCH for-4.14] x86/msr: Disallow access to Processor Trace MSRs

[Michał Leszczyński <michal.leszczynski@xxxxxxx>]

----- 19 cze 2020 o 14:49, Jan Beulich jbeulich@xxxxxxxx napisał(a):

> On 19.06.2020 14:10, Michał Leszczyński wrote:
>> ----- 19 cze 2020 o 13:58, Andrew Cooper andrew.cooper3@xxxxxxxxxx 
>> napisał(a):
>> 
>>> We do not expose the feature to guests, so should disallow access to the
>>> respective MSRs.
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> ---
>>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>>> CC: Wei Liu <wl@xxxxxxx>
>>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>> CC: Paul Durrant <paul@xxxxxxx>
>>> CC: Michał Leszczyński <michal.leszczynski@xxxxxxx>
>>>
>>> Paul: For 4.14.  This needs backporting to older trees as well.
>>>
>>> Michał: CC'ing, just to keep you in the loop.  Xen has some dubious default
>>> MSR semantics which we're still in the middle of untangling in a backwards
>>> compatible way.  Patches like this will eventually not be necessary, but 
>>> they
>>> are for now.
>> 
>> 
>> As for external IPT monitoring, it would be best if the VM would think
>> that IPT is simply not supported at all by the underlying hypervisor.
> 
> This is already the case, isn't it? Yet not reporting a feature may
> not keep a guest from trying to access the respective MSRs.
> 
> Jan


Okay, understood :)

ml