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
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