Re: Should SEV-ES #VC use IST? (Re: [PATCH] Allow RDTSC and RDTSCP from userspace)

Joerg Roedel
2020-06-23T12:12:44Z

On Tue, Jun 23, 2020 at 01:50:14PM +0200, Peter Zijlstra wrote:
> If SNP is the sole reason #VC needs to be IST, then I'd strongly urge
> you to only make it IST if/when you try and make SNP happen, not before.

It is not the only reason, when ES guests gain debug register support
then #VC also needs to be IST, because #DB can be promoted into #VC
then, and as #DB is IST for a reason, #VC needs to be too.

Besides that, I am not a fan of delegating problems I already see coming
to future-Joerg and future-Peter, but if at all possible deal with them
now and be safe later.

Regards,

Joerg