linux-kernel - Re: [PATCH 00/14] KVM: nVMX: Use vmcs_config for setting up nested VMX MSRs

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Date:   Mon, 27 Jun 2022 10:50:22 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/14] KVM: nVMX: Use vmcs_config for setting up nested
 VMX MSRs

On Mon, Jun 27, 2022 at 9:04 AM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> Changes since RFC:
> - "KVM: VMX: Extend VMX controls macro shenanigans" PATCH added and the
>   infrastructure is later used in other patches [Sean] PATCHes 1-3 added
>   to support the change.
> - "KVM: VMX: Clear controls obsoleted by EPT at runtime, not setup" PATCH
>   added [Sean].
> - Commit messages added.
>
> vmcs_config is a sanitized version of host VMX MSRs where some controls are
> filtered out (e.g. when Enlightened VMCS is enabled, some know bugs are
> discovered, some inconsistencies in controls are detected,...) but
> nested_vmx_setup_ctls_msrs() uses raw host MSRs instead. This may end up
> in exposing undesired controls to L1. Switch to using vmcs_config instead.
>
> Sean Christopherson (1):
>   KVM: VMX: Clear controls obsoleted by EPT at runtime, not setup
>
> Vitaly Kuznetsov (13):
>   KVM: VMX: Check VM_ENTRY_IA32E_MODE in setup_vmcs_config()
>   KVM: VMX: Check CPU_BASED_{INTR,NMI}_WINDOW_EXITING in
>     setup_vmcs_config()
>   KVM: VMX: Tweak the special handling of SECONDARY_EXEC_ENCLS_EXITING
>     in setup_vmcs_config()
>   KVM: VMX: Extend VMX controls macro shenanigans
>   KVM: VMX: Move CPU_BASED_CR8_{LOAD,STORE}_EXITING filtering out of
>     setup_vmcs_config()
>   KVM: VMX: Add missing VMEXIT controls to vmcs_config
>   KVM: VMX: Add missing VMENTRY controls to vmcs_config
>   KVM: VMX: Add missing CPU based VM execution controls to vmcs_config
>   KVM: nVMX: Use sanitized allowed-1 bits for VMX control MSRs
>   KVM: VMX: Store required-1 VMX controls in vmcs_config
>   KVM: nVMX: Use sanitized required-1 bits for VMX control MSRs
>   KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs_config
>   KVM: nVMX: Use cached host MSR_IA32_VMX_MISC value for setting up
>     nested MSR
>
>  arch/x86/kvm/vmx/capabilities.h |  16 +--
>  arch/x86/kvm/vmx/nested.c       |  37 +++---
>  arch/x86/kvm/vmx/nested.h       |   2 +-
>  arch/x86/kvm/vmx/vmx.c          | 198 ++++++++++++++------------------
>  arch/x86/kvm/vmx/vmx.h          | 118 +++++++++++++++++++
>  5 files changed, 229 insertions(+), 142 deletions(-)
>
> --
> 2.35.3
>

Just checking that this doesn't introduce any backwards-compatibility
issues. That is, all features that were reported as being available in
the past should still be available moving forward.

Thanks,

--jim