Re: [RFC PATCH 04/15] x86/pks: Preserve the PKRS MSR on context switch

[Peter Zijlstra]

On Tue, Jul 14, 2020 at 12:02:09AM -0700, ira.weiny@xxxxxxxxx wrote:
> From: Ira Weiny <ira.weiny@xxxxxxxxx>
> 
> The PKRS MSR is defined as a per-core register.  This isolates memory
> access by CPU.  Unfortunately, the MSR is not preserved by XSAVE.
> Therefore, We must preserve the protections for individual tasks even if
> they are context switched out and placed on another cpu later.

This is a contradiction and utter trainwreck. We're not going to do more
per-core MSRs and pretend they make sense per-task.