[PATCH v4 7/8] KVM: x86: Enable CMCI capability by default and handle injected UCNA errors

[Jue Wang <juew@google.com>]

Make KVM support the CMCI capability by default by adding MCG_CMCI_P to
kvm_mce_cap_supported. A vCPU can request for this capability via
KVM_X86_SETUP_MCE. Uncorrectable Error No Action required (UCNA) injection
reuses the MCE injection ioctl KVM_X86_SET_MCE.

Neither of the CMCI and UCNA emulations depends on hardware.

Signed-off-by: Jue Wang <juew@google.com>
---
 arch/x86/kvm/vmx/vmx.c |  1 +
 arch/x86/kvm/x86.c     | 50 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 610355b9ccce..1aed964ee4ee 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8037,6 +8037,7 @@ static __init int hardware_setup(void)
 	}
 
 	kvm_mce_cap_supported |= MCG_LMCE_P;
+	kvm_mce_cap_supported |= MCG_CMCI_P;
 
 	if (pt_mode != PT_MODE_SYSTEM && pt_mode != PT_MODE_HOST_GUEST)
 		return -EINVAL;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f8ab592f519b..d0b1bb6e5e4a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4826,6 +4826,52 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 	return r;
 }
 
+/*
+ * Validate this is an UCNA error by checking the MCG_STATUS and MCi_STATUS
+ * registers that none of the bits for Machine Check Exceptions are set and
+ * both the VAL (valid) and UC (uncorrectable) bits are set.
+ * UCNA - UnCorrectable No Action required
+ * SRAR - Software Recoverable Action Required
+ * MCI_STATUS_PCC - Processor Context Corrupted
+ * MCI_STATUS_S - Signaled as a Machine Check Exception
+ * MCI_STATUS_AR - This MCE is "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 mcg_cap = vcpu->arch.mcg_cap;
+	unsigned int bank_num = mcg_cap & 0xff;
+	u64 *banks = vcpu->arch.mce_banks;
+
+	if (mce->bank >= bank_num)
+		return -EINVAL;
+
+	if (!is_ucna(mce))
+		return -EINVAL;
+
+	banks += 4 * mce->bank;
+	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)
 {
@@ -4835,6 +4881,10 @@ static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
 
 	if (mce->bank >= bank_num || !(mce->status & MCI_STATUS_VAL))
 		return -EINVAL;
+
+	if (is_ucna(mce))
+		return kvm_vcpu_x86_set_ucna(vcpu, mce);
+
 	/*
 	 * if IA32_MCG_CTL is not all 1s, the uncorrected error
 	 * reporting is disabled
-- 
2.36.1.124.g0e6072fb45-goog