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Subject: Re: [PATCH 0/6] KVM: x86: KVM_SET_SREGS.CR4 bug fixes and cleanup
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Stas Sergeev <stsp@users.sourceforge.net>
References: <20201007014417.29276-1-sean.j.christopherson@intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <287166fd-0db1-ace1-3abe-96c5600fd30b@redhat.com>
Date:   Fri, 13 Nov 2020 12:36:13 +0100
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On 07/10/20 03:44, Sean Christopherson wrote:
> 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(-)
> 

Queued, thanks.

Paolo