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 13:08:39 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...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

On Tue, 2022-06-28 at 12:04 +0200, Vitaly Kuznetsov wrote:
> 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.
> 

Roger that!

Best regards,
	Maxim Levitsky