On Fri, Feb 14, 2025 at 09:10:05PM +0100, Borislav Petkov wrote: > On Thu, Feb 13, 2025 at 05:50:57PM +0000, Patrick Bellasi wrote: > > The "should be set identically across all processors in the system" makes me > > wondering if using the "KVM's user_return approach" proposed here is robust > > enough. Could this not lead to the bit being possibly set only on some CPU > > but not others? > > That's fine, we should update that paper. > > > If BpSpecReduce does not prevent training, but only the training from being > > used, should not we keep it consistently set after a guest has run, or until an > > IBPB is executed? > > After talking with folks internally, you're probably right. We should slap an > IBPB before clearing. Which means, I cannot use the MSR return slots anymore. > I will have to resurrect some of the other solutions we had lined up... > > Stay tuned. Thanks for working on this! Should this patch (and the two previously merged patches) be backported to stable? I noticed they did not have CC:stable. > > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
