[PATCH 04/11] KVM: x86: Disable MCE related stuff for TDX

[Xiaoyao Li]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

MCE is not supported for TDX VM and KVM cannot inject #MC to TDX VM.

Introduce kvm_guest_mce_disallowed() which actually reports the MCE
availability based on vm_type. And use it to guard all the MCE related
CAPs and IOCTLs.

Note: KVM_X86_GET_MCE_CAP_SUPPORTED is KVM scope so that what it reports
may not match the behavior of specific VM (e.g., here for TDX VM). The
same for KVM_CAP_MCE when queried from /dev/kvm. To qeuery the precise
KVM_CAP_MCE of the VM, it should use VM's fd.

[ Xiaoyao: Guard MCE related CAPs ]

Co-developed-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 arch/x86/kvm/x86.c | 10 ++++++++++
 arch/x86/kvm/x86.h |  5 +++++
 2 files changed, 15 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b02088343d80..2b21c5169f32 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4150,6 +4150,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 	case KVM_CAP_MCE:
 		r = KVM_MAX_MCE_BANKS;
+		if (kvm)
+			r = kvm_guest_mce_disallowed(kvm) ? 0 : r;
 		break;
 	case KVM_CAP_XCRS:
 		r = boot_cpu_has(X86_FEATURE_XSAVE);
@@ -5155,6 +5157,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	case KVM_X86_SETUP_MCE: {
 		u64 mcg_cap;
 
+		r = EINVAL;
+		if (kvm_guest_mce_disallowed(vcpu->kvm))
+			goto out;
+
 		r = -EFAULT;
 		if (copy_from_user(&mcg_cap, argp, sizeof(mcg_cap)))
 			goto out;
@@ -5164,6 +5170,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	case KVM_X86_SET_MCE: {
 		struct kvm_x86_mce mce;
 
+		r = EINVAL;
+		if (kvm_guest_mce_disallowed(vcpu->kvm))
+			goto out;
+
 		r = -EFAULT;
 		if (copy_from_user(&mce, argp, sizeof(mce)))
 			goto out;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index a2813892740d..69c60297bef2 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -441,6 +441,11 @@ static __always_inline bool kvm_irq_injection_disallowed(struct kvm_vcpu *vcpu)
 	return vcpu->kvm->arch.vm_type == KVM_X86_TDX_VM;
 }
 
+static __always_inline bool kvm_guest_mce_disallowed(struct kvm *kvm)
+{
+	return kvm->arch.vm_type == KVM_X86_TDX_VM;
+}
+
 void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
 void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
 int kvm_spec_ctrl_test_value(u64 value);
-- 
2.27.0