Messages in this thread | | | Date | Sat, 25 Apr 2020 22:23:16 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH] Allow RDTSC and RDTSCP from userspace |
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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).
Regards,
Joerg
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