linux-kernel - Re: [PATCH v2 03/21] KVM: x86: Add macros to track first...last VMX feature MSRs

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Date:   Wed, 15 Feb 2023 11:20:39 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Like Xu <like.xu.linux@...il.com>
Subject: Re: [PATCH v2 03/21] KVM: x86: Add macros to track first...last VMX
 feature MSRs

On 2/10/2023 8:31 AM, Sean Christopherson wrote:
> Add macros to track the range of VMX feature MSRs that are emulated by
> KVM to reduce the maintenance cost of extending the set of emulated MSRs.
> 
> Note, KVM doesn't necessarily emulate all known/consumed VMX MSRs, e.g.
> PROCBASED_CTLS3 is consumed by KVM to enable IPI virtualization, but is
> not emulated as KVM doesn't emulate/virtualize IPI virtualization for
> nested guests.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>

> ---
>   arch/x86/kvm/svm/svm.c | 2 +-
>   arch/x86/kvm/vmx/vmx.c | 8 ++++----
>   arch/x86/kvm/x86.h     | 8 ++++++++
>   3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index b43775490074..a5b9ebd6f2c5 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4107,7 +4107,7 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index)
>   {
>   	switch (index) {
>   	case MSR_IA32_MCG_EXT_CTL:
> -	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> +	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
>   		return false;
>   	case MSR_IA32_SMBASE:
>   		if (!IS_ENABLED(CONFIG_KVM_SMM))
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 47abd9101e68..ee86db130519 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1945,7 +1945,7 @@ static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx,
>   static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
>   {
>   	switch (msr->index) {
> -	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> +	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
>   		if (!nested)
>   			return 1;
>   		return vmx_get_vmx_msr(&vmcs_config.nested, msr->index, &msr->data);
> @@ -2030,7 +2030,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   		msr_info->data = to_vmx(vcpu)->msr_ia32_sgxlepubkeyhash
>   			[msr_info->index - MSR_IA32_SGXLEPUBKEYHASH0];
>   		break;
> -	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> +	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
>   		if (!nested_vmx_allowed(vcpu))
>   			return 1;
>   		if (vmx_get_vmx_msr(&vmx->nested.msrs, msr_info->index,
> @@ -2366,7 +2366,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   		vmx->msr_ia32_sgxlepubkeyhash
>   			[msr_index - MSR_IA32_SGXLEPUBKEYHASH0] = data;
>   		break;
> -	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> +	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
>   		if (!msr_info->host_initiated)
>   			return 1; /* they are read-only */
>   		if (!nested_vmx_allowed(vcpu))
> @@ -6960,7 +6960,7 @@ static bool vmx_has_emulated_msr(struct kvm *kvm, u32 index)
>   		 * real mode.
>   		 */
>   		return enable_unrestricted_guest || emulate_invalid_guest_state;
> -	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> +	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
>   		return nested;
>   	case MSR_AMD64_VIRT_SPEC_CTRL:
>   	case MSR_AMD64_TSC_RATIO:
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 754190af1791..4bc483d082ee 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -40,6 +40,14 @@ void kvm_spurious_fault(void);
>   	failed;								\
>   })
>   
> +/*
> + * The first...last VMX feature MSRs that are emulated by KVM.  This may or may
> + * not cover all known VMX MSRs, as KVM doesn't emulate an MSR until there's an
> + * associated feature that KVM supports for nested virtualization.
> + */
> +#define KVM_FIRST_EMULATED_VMX_MSR	MSR_IA32_VMX_BASIC
> +#define KVM_LAST_EMULATED_VMX_MSR	MSR_IA32_VMX_VMFUNC
> +
>   #define KVM_DEFAULT_PLE_GAP		128
>   #define KVM_VMX_DEFAULT_PLE_WINDOW	4096
>   #define KVM_DEFAULT_PLE_WINDOW_GROW	2