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

From: Paolo Bonzini
Date: Tue Sep 10 2024 - 06:09:45 EST


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; }