Re: [PATCH v2] x86/cpu: Fix migration safety with X86_BUG_NULL_SEL

[Sean Christopherson]

On Mon, Oct 18, 2021, Borislav Petkov wrote:
> On Mon, Oct 18, 2021 at 07:29:41PM +0000, Sean Christopherson wrote:
> > I agree.  If the argument for this patch is that the kernel can be migrated to
> > older hardware, then it stands to reason that the kernel could also be migrated
> > to a different CPU vendor entirely.  E.g. start on Intel, migrate to Zen1, kaboom.
> 
> Migration across vendors? Really, that works?
> 
> I'll believe it only when I see it with my own eyes.

There are plenty of caveats, but it is feasible.  KVM even has a few patches that
came about specifically to support cross-vendor migration, e.g. commit adc2a23734ac
("KVM: nSVM: improve SYSENTER emulation on AMD").