Re: [PATCH v7 06/13] KVM: x86: Add Intel Processor Trace virtualization mode

[Paolo Bonzini]

On 04/05/2018 12:45, Peter Zijlstra wrote:
> On Thu, May 03, 2018 at 04:38:23PM +0300, Alexander Shishkin wrote:
>> On Thu, May 03, 2018 at 02:50:12PM +0200, Paolo Bonzini wrote:
> 
>>> And you still need the module parameter to decide
>>> whether the host is _allowed_ to cause incomplete traces in the guest.
>>
>> Or rather a parameter to decide who wins in case both host and guest want
>> to trace the guest. That's arguably better than having different versions of
>> PT in the guest depending on a module parameter setting.
> 
> Yes, that sounds like a much better approach.

I don't think so.  The possibility that the host would lose tracing data
just because the guest starts using PT seems hideous to me...

Paolo