linux-kernel - [PATCH 0/6] KVM: x86: KVM_SET_SREGS.CR4 bug fixes and cleanup

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Message-Id: <20201007014417.29276-1-sean.j.christopherson@intel.com>
Date:   Tue,  6 Oct 2020 18:44:11 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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,
        Stas Sergeev <stsp@...rs.sourceforge.net>
Subject: [PATCH 0/6] KVM: x86: KVM_SET_SREGS.CR4 bug fixes and cleanup

Two bug fixes to handle KVM_SET_SREGS without a preceding KVM_SET_CPUID2.

The overarching issue is that kvm_x86_ops.set_cr4() can fail, but its
invocation from __set_sregs(), a.k.a. KVM_SET_SREGS, ignores the result.
Fix the issue by moving all validity checks out of .set_cr4() in one way
or another.

I intentionally omitted a Cc to stable.  The first bug fix in particular
may break stable trees as it simply removes a check, and I don't know that
stable trees have the generic CR4 reserved bit check that is needed to
prevent the guest from setting VMXE when nVMX is not allowed.

Sean Christopherson (6):
  KVM: VMX: Drop guest CPUID check for VMXE in vmx_set_cr4()
  KVM: VMX: Drop explicit 'nested' check from vmx_set_cr4()
  KVM: SVM: Drop VMXE check from svm_set_cr4()
  KVM: x86: Move vendor CR4 validity check to dedicated kvm_x86_ops hook
  KVM: x86: Return bool instead of int for CR4 and SREGS validity checks
  KVM: selftests: Verify supported CR4 bits can be set before
    KVM_SET_CPUID2

 arch/x86/include/asm/kvm_host.h               |  3 +-
 arch/x86/kvm/svm/nested.c                     |  2 +-
 arch/x86/kvm/svm/svm.c                        | 12 ++-
 arch/x86/kvm/svm/svm.h                        |  2 +-
 arch/x86/kvm/vmx/nested.c                     |  2 +-
 arch/x86/kvm/vmx/vmx.c                        | 35 +++----
 arch/x86/kvm/vmx/vmx.h                        |  2 +-
 arch/x86/kvm/x86.c                            | 28 +++---
 arch/x86/kvm/x86.h                            |  2 +-
 .../selftests/kvm/include/x86_64/processor.h  | 17 ++++
 .../selftests/kvm/include/x86_64/vmx.h        |  4 -
 .../selftests/kvm/x86_64/set_sregs_test.c     | 92 ++++++++++++++++++-
 12 files changed, 153 insertions(+), 48 deletions(-)

-- 
2.28.0