Re: [PATCH 2/9] KVM: x86: Emulate triple fault shutdown if RSM emulation fails

From: Paolo Bonzini
Date: Thu Jun 10 2021 - 09:23:35 EST

On 09/06/21 20:56, Sean Christopherson wrote:
For recent Intel CPUs, restoring NMI blocking is technically wrong, but
so is restoring NMI blocking in the first place, and Intel's RSM
"architecture" is such a mess that just about anything is allowed and can
be justified as micro-architectural behavior.

The Intel manual is an absolute mess with respect to NMI blocking, and for once AMD followed suit.

Some versions of the AMD BIOS and Kernel Developer Manual provide the offset of the "NMI masked" flag in the SMM state save area, but unfortunately that was discovered too late.