Re: [PATCH] KVM: x86: Expose Predictive Store Forwarding Disable

From: Paolo Bonzini
Date: Mon Sep 27 2021 - 08:16:12 EST

On 27/09/21 14:06, Borislav Petkov wrote:
Because the guest kernel needs to know which MSRs to write when you touch
the SSBD prctl, so that PSFD is properly disabled*inside the guest*.
It already knows which - the same one which disables SSB. PSF is
disabled*together* with SSB, for now...

Right, not which MSR to write but which value to write. It doesn't know that the PSF disable bit is valid unless the corresponding CPUID bit is set.