On 3/20/20 6:17 AM, Joerg Roedel wrote:

On Thu, Mar 19, 2020 at 08:35:59AM -0700, Andy Lutomirski wrote:

quoted

1. Just put the NMI unmask in do_nmi().  The kernel *already* knows
how to handle running do_nmi() with NMIs unmasked.  This is much, much
simpler than your code.

Okay, attached is the updated patch which implements this approach. I
tested it in an SEV-ES guest with 'perf top' running for a little more
than 30 minutes and all looked good. I also removed the dead code from
the patch.

FWIW, perf plus the x86 selftests run in a big loop was my best way of
stressing the NMI path when we mucked with it for PTI.  The selftests
make sure to hit some of the more rare entry/exit paths.