linux-kernel - Re: [PATCH v2 20/28] KVM: VMX: Add missing VMENTRY controls to vmcs

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Date:   Fri, 1 Jul 2022 09:01:35 -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 v2 20/28] KVM: VMX: Add missing VMENTRY controls to vmcs_config

On Wed, Jun 29, 2022 at 8:07 AM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> As a preparation to reusing the result of setup_vmcs_config() in
> nested VMX MSR setup, add the VMENTRY controls which KVM doesn't
> use but supports for nVMX to KVM_OPT_VMX_VM_ENTRY_CONTROLS and
> filter them out in vmx_vmentry_ctrl().
>
> No functional change intended.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 3 +++
>  arch/x86/kvm/vmx/vmx.h | 4 +++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e5ab77ed37e4..b774b6391e0e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -4179,6 +4179,9 @@ static u32 vmx_vmentry_ctrl(void)
>  {
>         u32 vmentry_ctrl = vmcs_config.vmentry_ctrl;
>
> +       /* Not used by KVM but supported for nesting. */
> +       vmentry_ctrl &= ~(VM_ENTRY_SMM | VM_ENTRY_DEACT_DUAL_MONITOR);
> +

LOL! KVM does not emulate the dual-monitor treatment of SMIs and SMM.
Do we actually claim to support these VM-entry controls today?!?

>         if (vmx_pt_mode_is_system())
>                 vmentry_ctrl &= ~(VM_ENTRY_PT_CONCEAL_PIP |
>                                   VM_ENTRY_LOAD_IA32_RTIT_CTL);
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index d4503a38735b..7ada8410a037 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -479,7 +479,9 @@ static inline u8 vmx_get_rvi(void)
>                 __KVM_REQ_VMX_VM_ENTRY_CONTROLS
>  #endif
>  #define KVM_OPT_VMX_VM_ENTRY_CONTROLS                          \
> -       (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL |                  \
> +       (VM_ENTRY_SMM |                                         \
> +       VM_ENTRY_DEACT_DUAL_MONITOR |                           \
> +       VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL |                   \
>         VM_ENTRY_LOAD_IA32_PAT |                                \
>         VM_ENTRY_LOAD_IA32_EFER |                               \
>         VM_ENTRY_LOAD_BNDCFGS |                                 \
> --
> 2.35.3
>