Re: [PATCH v2 6/8] KVM: x86: compile out vendor-specific code if SMM is disabled

From: Maxim Levitsky
Date: Mon Oct 24 2022 - 15:23:43 EST

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On Thu, 2022-09-29 at 13:20 -0400, Paolo Bonzini wrote:
> Vendor-specific code that deals with SMI injection and saving/restoring
> SMM state is not needed if CONFIG_KVM_SMM is disabled, so remove the
> four callbacks smi_allowed, enter_smm, leave_smm and enable_smi_window.
> The users in svm/nested.c and x86.c also have to be compiled out; the
> amount of #ifdef'ed code is small and it's not worth moving it to
> smm.c.
>
> enter_smm is now used only within #ifdef CONFIG_KVM_SMM, and the stub
> can therefore be removed.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm-x86-ops.h | 2 ++
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/smm.h | 1 -
> arch/x86/kvm/svm/nested.c | 2 ++
> arch/x86/kvm/svm/svm.c | 4 ++++
> arch/x86/kvm/vmx/vmx.c | 4 ++++
> arch/x86/kvm/x86.c | 4 ++++
> 7 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 82ba4a564e58..ea58e67e9a67 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -110,10 +110,12 @@ KVM_X86_OP_OPTIONAL_RET0(dy_apicv_has_pending_interrupt)
> KVM_X86_OP_OPTIONAL(set_hv_timer)
> KVM_X86_OP_OPTIONAL(cancel_hv_timer)
> KVM_X86_OP(setup_mce)
> +#ifdef CONFIG_KVM_SMM
> KVM_X86_OP(smi_allowed)
> KVM_X86_OP(enter_smm)
> KVM_X86_OP(leave_smm)
> KVM_X86_OP(enable_smi_window)
> +#endif
> KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
> KVM_X86_OP_OPTIONAL(mem_enc_register_region)
> KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index b7d078cd768d..cb88da02d965 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1606,10 +1606,12 @@ struct kvm_x86_ops {
>
> void (*setup_mce)(struct kvm_vcpu *vcpu);
>
> +#ifdef CONFIG_KVM_SMM
> int (*smi_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
> int (*enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
> int (*leave_smm)(struct kvm_vcpu *vcpu, const char *smstate);
> void (*enable_smi_window)(struct kvm_vcpu *vcpu);
> +#endif
>
> int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp);
> int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp);
> diff --git a/arch/x86/kvm/smm.h b/arch/x86/kvm/smm.h
> index 4c699fee4492..7ccce6b655ca 100644
> --- a/arch/x86/kvm/smm.h
> +++ b/arch/x86/kvm/smm.h
> @@ -28,7 +28,6 @@ void process_smi(struct kvm_vcpu *vcpu);
> static inline int kvm_inject_smi(struct kvm_vcpu *vcpu) { return -ENOTTY; }
> static inline bool is_smm(struct kvm_vcpu *vcpu) { return false; }
> static inline void kvm_smm_changed(struct kvm_vcpu *vcpu, bool in_smm) { WARN_ON_ONCE(1); }
> -static inline void enter_smm(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(1); }
> static inline void process_smi(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(1); }
>
> /*
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index cc0fd75f7cba..b258d6988f5d 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1378,6 +1378,7 @@ static int svm_check_nested_events(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +#ifdef CONFIG_KVM_SMM
> if (vcpu->arch.smi_pending && !svm_smi_blocked(vcpu)) {
> if (block_nested_events)
> return -EBUSY;
> @@ -1386,6 +1387,7 @@ static int svm_check_nested_events(struct kvm_vcpu *vcpu)
> nested_svm_simple_vmexit(svm, SVM_EXIT_SMI);
> return 0;
> }
> +#endif
>
> if (vcpu->arch.nmi_pending && !svm_nmi_blocked(vcpu)) {
> if (block_nested_events)
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 6f7ceb35d2ff..2200b8aa7273 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4408,6 +4408,7 @@ static void svm_setup_mce(struct kvm_vcpu *vcpu)
> vcpu->arch.mcg_cap &= 0x1ff;
> }
>
> +#ifdef CONFIG_KVM_SMM
> bool svm_smi_blocked(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> @@ -4557,6 +4558,7 @@ static void svm_enable_smi_window(struct kvm_vcpu *vcpu)
> /* We must be in SMM; RSM will cause a vmexit anyway. */
> }
> }
> +#endif
>
> static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
> void *insn, int insn_len)
> @@ -4832,10 +4834,12 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> .pi_update_irte = avic_pi_update_irte,
> .setup_mce = svm_setup_mce,
>
> +#ifdef CONFIG_KVM_SMM
> .smi_allowed = svm_smi_allowed,
> .enter_smm = svm_enter_smm,
> .leave_smm = svm_leave_smm,
> .enable_smi_window = svm_enable_smi_window,
> +#endif
>
> .mem_enc_ioctl = sev_mem_enc_ioctl,
> .mem_enc_register_region = sev_mem_enc_register_region,
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index b22330a15adb..107fc035c91b 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7905,6 +7905,7 @@ static void vmx_setup_mce(struct kvm_vcpu *vcpu)
> ~FEAT_CTL_LMCE_ENABLED;
> }
>
> +#ifdef CONFIG_KVM_SMM
> static int vmx_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
> {
> /* we need a nested vmexit to enter SMM, postpone if run is pending */
> @@ -7959,6 +7960,7 @@ static void vmx_enable_smi_window(struct kvm_vcpu *vcpu)
> {
> /* RSM will cause a vmexit anyway. */
> }
> +#endif
>
> static bool vmx_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
> {
> @@ -8126,10 +8128,12 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
>
> .setup_mce = vmx_setup_mce,
>
> +#ifdef CONFIG_KVM_SMM
> .smi_allowed = vmx_smi_allowed,
> .enter_smm = vmx_enter_smm,
> .leave_smm = vmx_leave_smm,
> .enable_smi_window = vmx_enable_smi_window,
> +#endif
>
> .can_emulate_instruction = vmx_can_emulate_instruction,
> .apic_init_signal_blocked = vmx_apic_init_signal_blocked,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a9e050aefea6..e22184bad92b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9863,6 +9863,7 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
> * in order to make progress and get back here for another iteration.
> * The kvm_x86_ops hooks communicate this by returning -EBUSY.
> */
> +#ifdef CONFIG_KVM_SMM
> if (vcpu->arch.smi_pending) {
> r = can_inject ? static_call(kvm_x86_smi_allowed)(vcpu, true) : -EBUSY;
> if (r < 0)
> @@ -9875,6 +9876,7 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
> } else
> static_call(kvm_x86_enable_smi_window)(vcpu);
> }
> +#endif
>
> if (vcpu->arch.nmi_pending) {
> r = can_inject ? static_call(kvm_x86_nmi_allowed)(vcpu, true) : -EBUSY;
> @@ -12491,10 +12493,12 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
> static_call(kvm_x86_nmi_allowed)(vcpu, false)))
> return true;
>
> +#ifdef CONFIG_KVM_SMM
> if (kvm_test_request(KVM_REQ_SMI, vcpu) ||
> (vcpu->arch.smi_pending &&
> static_call(kvm_x86_smi_allowed)(vcpu, false)))
> return true;
> +#endif
>
> if (kvm_arch_interrupt_allowed(vcpu) &&
> (kvm_cpu_has_interrupt(vcpu) ||

Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>

Best regards,
Maxim Levitsky

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