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

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Date:   Tue, 28 Jun 2022 12:04:02 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH 00/14] KVM: nVMX: Use vmcs_config for setting up nested
 VMX MSRs

Maxim Levitsky <mlevitsk@...hat.com> writes:

> On Mon, 2022-06-27 at 18:04 +0200, Vitaly Kuznetsov 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(-)
>> 
> Sorry that I was a bit out of loop on this, so before I review it,
> does this patch series solve the eVMCS issue we had alone,
> or we still need the eVMCS version patch series as well?

"[PATCH 00/11] KVM: VMX: Support TscScaling and EnclsExitingBitmap whith
eVMCS" adds new features, namely TSC scaling for both KVM-on-Hyper-V and
Hyper-V-on-KVM. This series doesn't add any features but avoids the
problem reported by Anirudh by properly filtering values in L1 VMX MSRs.

TL;DR: Both series are needed.

-- 
Vitaly