KVM: x86: Enable CMCI capability by default and handle injected UCNA errors

This patch enables MCG_CMCI_P by default in kvm_mce_cap_supported. It
reuses ioctl KVM_X86_SET_MCE to implement injection of UnCorrectable
No Action required (UCNA) errors, signaled via Corrected Machine
Check Interrupt (CMCI).

Neither of the CMCI and UCNA emulations depends on hardware.

Signed-off-by: Jue Wang <juew@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220610171134.772566-8-juew@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -8299,6 +8299,7 @@ static __init int hardware_setup(void)
 	}
 
 	kvm_caps.supported_mce_cap |= MCG_LMCE_P;
+	kvm_caps.supported_mce_cap |= MCG_CMCI_P;
 
 	if (pt_mode != PT_MODE_SYSTEM && pt_mode != PT_MODE_HOST_GUEST)
 		return -EINVAL;

arch/x86/kvm/x86.c

@@ -4901,6 +4901,42 @@ out:
 	return r;
 }
 
+/*
+ * Validate this is an UCNA (uncorrectable no action) error by checking the
+ * MCG_STATUS and MCi_STATUS registers:
+ * - none of the bits for Machine Check Exceptions are set
+ * - both the VAL (valid) and UC (uncorrectable) bits are set
+ * MCI_STATUS_PCC - Processor Context Corrupted
+ * MCI_STATUS_S - Signaled as a Machine Check Exception
+ * MCI_STATUS_AR - Software recoverable Action Required
+ */
+static bool is_ucna(struct kvm_x86_mce *mce)
+{
+	return	!mce->mcg_status &&
+		!(mce->status & (MCI_STATUS_PCC | MCI_STATUS_S | MCI_STATUS_AR)) &&
+		(mce->status & MCI_STATUS_VAL) &&
+		(mce->status & MCI_STATUS_UC);
+}
+
+static int kvm_vcpu_x86_set_ucna(struct kvm_vcpu *vcpu, struct kvm_x86_mce *mce, u64* banks)
+{
+	u64 mcg_cap = vcpu->arch.mcg_cap;
+
+	banks[1] = mce->status;
+	banks[2] = mce->addr;
+	banks[3] = mce->misc;
+	vcpu->arch.mcg_status = mce->mcg_status;
+
+	if (!(mcg_cap & MCG_CMCI_P) ||
+	    !(vcpu->arch.mci_ctl2_banks[mce->bank] & MCI_CTL2_CMCI_EN))
+		return 0;
+
+	if (lapic_in_kernel(vcpu))
+		kvm_apic_local_deliver(vcpu->arch.apic, APIC_LVTCMCI);
+
+	return 0;
+}
+
 static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
 				      struct kvm_x86_mce *mce)
 {
@@ -4910,6 +4946,12 @@ static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
 
 	if (mce->bank >= bank_num || !(mce->status & MCI_STATUS_VAL))
 		return -EINVAL;
+
+	banks += array_index_nospec(4 * mce->bank, 4 * bank_num);
+
+	if (is_ucna(mce))
+		return kvm_vcpu_x86_set_ucna(vcpu, mce, banks);
+
 	/*
 	 * if IA32_MCG_CTL is not all 1s, the uncorrected error
 	 * reporting is disabled
@@ -4917,7 +4959,6 @@ static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
 	if ((mce->status & MCI_STATUS_UC) && (mcg_cap & MCG_CTL_P) &&
 	    vcpu->arch.mcg_ctl != ~(u64)0)
 		return 0;
-	banks += 4 * mce->bank;
 	/*
 	 * if IA32_MCi_CTL is not all 1s, the uncorrected error
 	 * reporting is disabled for the bank