On Thu, Mar 19, 2020 at 02:27:49PM -0700, Andy Lutomirski wrote: > AIUI the shift-ist stuff is because we aren't very good about the way > that we handle tracing right now, and that can cause a limited degree > of recursion. #DB uses IST for historical reasons that don't > necessarily make sense. Right now, we need it for only one reason: > the MOV SS issue. IIRC this isn't actually triggerable without > debugging enabled -- MOV SS with no breakpoint but TF on doesn't seem > to malfunction quite as badly. I had a look at the shift_ist stuff today and it looks like a good solution to the #VC nesting problem when it is turned into a #VC handler. The devil is in the details, of course, as 3 or 4 stacks for the #VC handler (per cpu) should only be allocated when actually running in an SEV-ES guest. Let's see how this works out in practice. Regards, Joerg
