linux-kernel - Re: [PATCH 0/2] KVM: VMX: Fix and test for emulation + exception

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Date:   Tue, 18 Jan 2022 10:25:35 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     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,
        syzbot+82112403ace4cbd780d8@...kaller.appspotmail.com
Subject: Re: [PATCH 0/2] KVM: VMX: Fix and test for emulation + exception

On 12/29/21 00:24, Sean Christopherson wrote:
> Fix an issue that allows userspace to trigger a WARN by rejecting KVM_RUN
> if userspace attempts to run a vCPU that require emulation in KVM and has
> a pending exception, which is not supported in KVM.
> 
> No small part of me thinks this is a waste of code and that we'd be better
> off just deleting the WARN.  But it's also not hard to fix and there are
> still folks out there that run on Core2...
> 
> Intentionally didn't tag for stable.  I highly doubt this actually fixes
> anything for anyone, the goal is purely to prevent userspace from triggering
> the WARN.
> 
> Sean Christopherson (2):
>    KVM: VMX: Reject KVM_RUN if emulation is required with pending
>      exception
>    KVM: selftests: Add a test to force emulation with a pending exception
> 
>   arch/x86/include/asm/kvm-x86-ops.h            |   1 +
>   arch/x86/include/asm/kvm_host.h               |   1 +
>   arch/x86/kvm/svm/svm.c                        |   6 +
>   arch/x86/kvm/vmx/vmx.c                        |  22 ++-
>   arch/x86/kvm/x86.c                            |  12 +-
>   tools/testing/selftests/kvm/.gitignore        |   1 +
>   tools/testing/selftests/kvm/Makefile          |   1 +
>   .../vmx_exception_with_invalid_guest_state.c  | 139 ++++++++++++++++++
>   8 files changed, 178 insertions(+), 5 deletions(-)
>   create mode 100644 tools/testing/selftests/kvm/x86_64/vmx_exception_with_invalid_guest_state.c
> 

Queued, thanks.

Paolo