On Tue, Jul 14, 2020 at 09:05:39PM +0200, Peter Zijlstra wrote: > On Tue, Jul 14, 2020 at 11:53:22AM -0700, Ira Weiny wrote: > > On Tue, Jul 14, 2020 at 10:27:01AM +0200, Peter Zijlstra wrote: > > > 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. > > > > I don't understand where there is a contradiction? Perhaps I should have said > > the MSR is not XSAVE managed vs 'preserved'? > > You're stating the MSR is per-*CORE*, and then continue to talk about > per-task state. > > We've had a bunch of MSRs have exactly that problem recently, and it's > not fun. We're not going to do that again. Ah sorry, my mistake yes I meant 'per-logical-processor' like Dave said. I'll update the commit message. Ira
