On Sat, Apr 25, 2020 at 1:23 PM Joerg Roedel <joro@xxxxxxxxxx> wrote: > > On Sat, Apr 25, 2020 at 12:47:31PM -0700, Andy Lutomirski wrote: > > I assume the race you mean is: > > > > #VC > > Immediate NMI before IST gets shifted > > #VC > > > > Kaboom. > > > > How are you dealing with this? Ultimately, I think that NMI will need > > to turn off IST before engaging in any funny business. Let me ponder > > this a bit. > > Right, I dealt with that by unconditionally shifting/unshifting the #VC IST entry > in do_nmi() (thanks to Davin Kaplan for the idea). It might cause > one of the IST stacks to be unused during nesting, but that is fine. The > stack memory for #VC is only allocated when SEV-ES is active (in an > SEV-ES VM). Blech. It probably works, but still, yuck. It's a bit sad that we seem to be growing more and more poorly designed happens-anywhere exception types at an alarming rate. We seem to have #NM, #MC, #VC, #HV, and #DB. This doesn't really scale. --Andy
