Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active

From: Paolo Bonzini
Date: Tue Sep 11 2018 - 10:00:31 EST

On 11/09/2018 15:55, Borislav Petkov wrote:
> On Tue, Sep 11, 2018 at 01:07:06PM +0200, Paolo Bonzini wrote:
>> If the host TSCs are unsynchronized then yes, that's what happens. And
>> you can do live migration from synchronized to unsynchronized.
> Which brings us back to my original question: why would we *ever* want
> to support unsynchronized TSCs in a guest? Such machines are a real
> abomination for baremetal - it doesn't make *any* sense to me to have
> that in guests too, if it can be helped...

No, wait. The host TSC is unsynchronized, _so_ you need one kvmclock
struct per vCPU. The resulting kvmclock is synchronized.