linux-kernel - [PATCH v2 0/4] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

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Message-ID: <20230825013621.2845700-1-seanjc@google.com>
Date:   Thu, 24 Aug 2023 18:36:17 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wu Zongyo <wuzongyo@...l.ustc.edu.cn>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH v2 0/4] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

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.

Patch 1 is the main fix.  It's a little ugly, but suitable for backporting.

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.

Patches 3 and 4 clean up the hack from patch 1, but are most definitely
not stable material (hence the slightly ugly fix).

Verified the original bug by toggling the NX hugepage mitigation to force
a #NPF when devliering #BP in the guest.

v2:
 - Actually fix the bug. [Tom]
 - Do the bigger cleanup I avoided in v1.

v1: https://lore.kernel.org/all/20230810234919.145474-1-seanjc@google.com

Sean Christopherson (4):
  KVM: SVM: Don't inject #UD if KVM attempts to skip SEV guest insn
  KVM: SVM: Require nrips support for SEV guests (and beyond)
  KVM: x86: Refactor can_emulate_instruction() return to be more
    expressive
  KVM: SVM: Treat all "skip" emulation for SEV guests as outright
    failures

 arch/x86/include/asm/kvm-x86-ops.h |  2 +-
 arch/x86/include/asm/kvm_host.h    |  4 +--
 arch/x86/kvm/svm/sev.c             |  2 +-
 arch/x86/kvm/svm/svm.c             | 55 +++++++++++++++++-------------
 arch/x86/kvm/svm/svm.h             |  1 +
 arch/x86/kvm/vmx/vmx.c             | 12 +++----
 arch/x86/kvm/x86.c                 | 22 ++++++++----
 7 files changed, 58 insertions(+), 40 deletions(-)

base-commit: fff2e47e6c3b8050ca26656693caa857e3a8b740
-- 
2.42.0.rc2.253.gd59a3bf2b4-goog