[PATCH v15 099/115] KVM: TDX: Handle MSR IA32_FEAT_CTL MSR and IA32_MCG_EXT_CTL

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

MCE and MCA is advertised via cpuid based on the TDX module spec.  Guest
kernel can access IA32_FEAT_CTL for checking if LMCE is enabled by platform
and IA32_MCG_EXT_CTL to enable LMCE.  Make TDX KVM handle them.  Otherwise
guest MSR access to them with TDG.VP.VMCALL<MSR> on VE results in GP in
guest.

Because LMCE is disabled with qemu by default, "-cpu lmce=on" to qemu
command line is needed to reproduce it.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/kvm/vmx/tdx.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 3775db455f29..77052f49481a 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1806,6 +1806,7 @@ bool tdx_has_emulated_msr(u32 index, bool write)
 		default:
 			return true;
 		}
+	case MSR_IA32_FEAT_CTL:
 	case MSR_IA32_APICBASE:
 	case MSR_EFER:
 		return !write;
@@ -1820,6 +1821,20 @@ bool tdx_has_emulated_msr(u32 index, bool write)
 int tdx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	switch (msr->index) {
+	case MSR_IA32_FEAT_CTL:
+		/*
+		 * MCE and MCA are advertised via cpuid. guest kernel could
+		 * check if LMCE is enabled or not.
+		 */
+		msr->data = FEAT_CTL_LOCKED;
+		if (vcpu->arch.mcg_cap & MCG_LMCE_P)
+			msr->data |= FEAT_CTL_LMCE_ENABLED;
+		return 0;
+	case MSR_IA32_MCG_EXT_CTL:
+		if (!msr->host_initiated && !(vcpu->arch.mcg_cap & MCG_LMCE_P))
+			return 1;
+		msr->data = vcpu->arch.mcg_ext_ctl;
+		return 0;
 	case MSR_MTRRcap:
 		/*
 		 * Override kvm_mtrr_get_msr() which hardcodes the value.
@@ -1838,6 +1853,11 @@ int tdx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 int tdx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	switch (msr->index) {
+	case MSR_IA32_MCG_EXT_CTL:
+		if (!msr->host_initiated && !(vcpu->arch.mcg_cap & MCG_LMCE_P))
+			return 1;
+		vcpu->arch.mcg_ext_ctl = msr->data;
+		return 0;
 	case MSR_MTRRdefType:
 		/*
 		 * Allow writeback only for all memory.
-- 
2.25.1