linux-kernel - [PATCH 0/2] KVM: x86: Emulate L2 triple fault without killing L1

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Date:   Tue,  2 Mar 2021 09:45:13 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH 0/2] KVM: x86: Emulate L2 triple fault without killing L1

If KVM (L0) intercepts #GP, but L1 does not, then L2 can kill L1 by
triggering triple fault.  On both VMX and SVM, if the CPU hits a fault
while vectoring an injected #DF (or I supposed any #DF), any intercept
from the hypervisor takes priority over triple fault.  #PF is unlikely to
be intercepted by L0 but not L1.  The bigger problem is #GP, which is
intercepted on both VMX and SVM if enable_vmware_backdoor=1, and is also
now intercepted for the lovely VMRUN/VMLOAD/VMSAVE errata.

Based on kvm/queue, commit fe5f0041c026 ("KVM/SVM: Move vmenter.S exception
fixups out of line").  x86.c and svm/nested.c conflict with kvm/master.
They are minor and straighforward, but let me know if you want me to post
a version based on kvm/master for easier inclusion into 5.12.

Sean Christopherson (2):
  KVM: x86: Handle triple fault in L2 without killing L1
  KVM: nSVM: Add helper to synthesize nested VM-Exit without collateral

 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/lapic.c            |  2 +-
 arch/x86/kvm/svm/nested.c       | 57 ++++++++-------------------------
 arch/x86/kvm/svm/svm.c          |  6 +---
 arch/x86/kvm/svm/svm.h          |  9 ++++++
 arch/x86/kvm/vmx/nested.c       |  9 ++++++
 arch/x86/kvm/x86.c              | 29 +++++++++++++----
 arch/x86/kvm/x86.h              |  2 ++
 8 files changed, 60 insertions(+), 55 deletions(-)

-- 
2.30.1.766.gb4fecdf3b7-goog