Re: [PATCH 17/21] KVM: TDX: MTRR: implement get_mt_mask() for TDX

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 9/4/24 05:07, Rick Edgecombe wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Although TDX supports only WB for private GPA, it's desirable to support
> MTRR for shared GPA.  Always honor guest PAT for shared EPT as what's done
> for normal VMs.
>
> Suggested-by: Kai Huang <kai.huang@xxxxxxxxx>
> Co-developed-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> ---
> TDX MMU part 2 v1:
>   - Align with latest vmx code in kvm/queue.
>   - Updated patch log.
>   - Dropped KVM_BUG_ON() in vt_get_mt_mask(). (Rick)

The only difference at this point is

        if (!static_cpu_has(X86_FEATURE_SELFSNOOP) &&
            !kvm_arch_has_noncoherent_dma(vcpu->kvm))
                return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT) | 
VMX_EPT_IPAT_BIT;


which should never be true.  I think this patch can simply be dropped.

Paolo

> +static u8 vt_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> +{
> +	if (is_td_vcpu(vcpu))
> +		return tdx_get_mt_mask(vcpu, gfn, is_mmio);
> +
> +	return vmx_get_mt_mask(vcpu, gfn, is_mmio);
> +}
> +
>   static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
>   {
>   	if (!is_td(kvm))
> @@ -292,7 +300,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>   
>   	.set_tss_addr = vmx_set_tss_addr,
>   	.set_identity_map_addr = vmx_set_identity_map_addr,
> -	.get_mt_mask = vmx_get_mt_mask,
> +	.get_mt_mask = vt_get_mt_mask,
>   
>   	.get_exit_info = vmx_get_exit_info,
>   
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 435112562954..50ce24905062 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -374,6 +374,14 @@ int tdx_vm_init(struct kvm *kvm)
>   	return 0;
>   }
>   
> +u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> +{
> +	if (is_mmio)
> +		return MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT;
> +
> +	return MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT;
> +}
> +
>   int tdx_vcpu_create(struct kvm_vcpu *vcpu)
>   {
>   	struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 66829413797d..d8a00ab4651c 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -128,6 +128,7 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp);
>   int tdx_vcpu_create(struct kvm_vcpu *vcpu);
>   void tdx_vcpu_free(struct kvm_vcpu *vcpu);
>   void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
> +u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
>   
>   int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
>   
> @@ -153,6 +154,7 @@ static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOP
>   static inline int tdx_vcpu_create(struct kvm_vcpu *vcpu) { return -EOPNOTSUPP; }
>   static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {}
>   static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {}
> +static inline u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) { return 0; }
>   
>   static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
>