Re: [PATCH 15/28] KVM: VMX: enable use of MBEC

[Sean Christopherson <seanjc@google.com>]

On Thu, Apr 30, 2026, Paolo Bonzini wrote:
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 337bbfecc021..72a75fa33c93 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -114,6 +114,9 @@ module_param(emulate_invalid_guest_state, bool, 0444);
>  static bool __read_mostly fasteoi = 1;
>  module_param(fasteoi, bool, 0444);
>  
> +bool __read_mostly enable_mbec = 1;
> +module_param_named(mbec, enable_mbec, bool, 0444);
> +

...

> @@ -7823,6 +7830,11 @@ u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
>  	return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT);
>  }
>  
> +bool vmx_tdp_has_smep(struct kvm *kvm)
> +{
> +	return enable_mbec;

Given that enable_mbec is made visible for nested.c anyways, I don't see any
reason to trampoline into vmx.c.  Ugh, never mind, because VMX needs to provide
a function for the ops hook when TDX support is disabled.

We could at least make vmx_tdp_has_smep() a static inline though.

> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index d09abeac2b56..69cf276be88e 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -103,6 +103,7 @@ void vmx_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap);
>  int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr);
>  int vmx_set_identity_map_addr(struct kvm *kvm, u64 ident_addr);
>  u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
> +bool vmx_tdp_has_smep(struct kvm *kvm);
>  
>  void vmx_get_exit_info(struct kvm_vcpu *vcpu, u32 *reason,
>  		       u64 *info1, u64 *info2, u32 *intr_info, u32 *error_code);
> -- 
> 2.52.0
> 
>