Re: [PATCH 0/2] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

[Tom Lendacky]

On 8/10/23 18:49, Sean Christopherson wrote:
> Fix a bug where KVM injects a bogus #UD for SEV guests when trying to skip
> an INT3 as part of re-injecting the associated #BP that got kinda sorta
> intercepted due to a #NPF occuring while vectoring/delivering the #BP.
>
> I haven't actually confirmed that patch 1 fixes the bug, as it's a
> different change than what I originally proposed.  I'm 99% certain it will
> work, but I definitely need verification that it fixes the problem
>
> Patch 2 is a tangentially related cleanup to make NRIPS a requirement for
> enabling SEV, e.g. so that we don't ever get "bug" reports of SEV guests
> not working when NRIPS is disabled.
>
> Sean Christopherson (2):
>    KVM: SVM: Don't inject #UD if KVM attempts emulation of SEV guest w/o
>      insn
>    KVM: SVM: Require nrips support for SEV guests (and beyond)
>
>   arch/x86/kvm/svm/sev.c |  2 +-
>   arch/x86/kvm/svm/svm.c | 37 ++++++++++++++++++++-----------------
>   arch/x86/kvm/svm/svm.h |  1 +
>   3 files changed, 22 insertions(+), 18 deletions(-)

We ran some stress tests against a version of the kernel without this fix 
and we're able to reproduce the issue, but not reliably, after a few 
hours. With this patch, it has not reproduced after running for a week.

Not as reliable a scenario as the original reporter, but this looks like 
it resolves the issue.

So, for the series:

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

> base-commit: 240f736891887939571854bd6d734b6c9291f22e