Emulate machine check related MSRs to allow guest OSes like Windows to boot.

Reported by:	Leon Dang (ldang@nahannisys.com)
MFC after:	2 weeks

3 files changed, 24 insertions, 7 deletions

diff --git a/sys/amd64/vmm/amd/svm_msr.c b/sys/amd64/vmm/amd/svm_msr.c
index d3a6fe8..088751a 100644
--- a/sys/amd64/vmm/amd/svm_msr.c
+++ b/sys/amd64/vmm/amd/svm_msr.c
@@ -110,6 +110,10 @@ svm_rdmsr(struct svm_softc *sc, int vcpu, u_int num, uint64_t *result,
 	int error = 0;
 
 	switch (num) {
+	case MSR_MCG_CAP:
+	case MSR_MCG_STATUS:
+		*result = 0;
+		break;
 	case MSR_MTRRcap:
 	case MSR_MTRRdefType:
 	case MSR_MTRR4kBase ... MSR_MTRR4kBase + 8:
@@ -135,6 +139,9 @@ svm_wrmsr(struct svm_softc *sc, int vcpu, u_int num, uint64_t val, bool *retu)
 	int error = 0;
 
 	switch (num) {
+	case MSR_MCG_CAP:
+	case MSR_MCG_STATUS:
+		break;		/* ignore writes */
 	case MSR_MTRRcap:
 		vm_inject_gp(sc->vm, vcpu);
 		break;
diff --git a/sys/amd64/vmm/intel/vmx_msr.c b/sys/amd64/vmm/intel/vmx_msr.c
index 526b0d1..3091f68 100644
--- a/sys/amd64/vmm/intel/vmx_msr.c
+++ b/sys/amd64/vmm/intel/vmx_msr.c
@@ -395,6 +395,10 @@ vmx_rdmsr(struct vmx *vmx, int vcpuid, u_int num, uint64_t *val, bool *retu)
 	error = 0;
 
 	switch (num) {
+	case MSR_MCG_CAP:
+	case MSR_MCG_STATUS:
+		*val = 0;
+		break;
 	case MSR_MTRRcap:
 	case MSR_MTRRdefType:
 	case MSR_MTRR4kBase ... MSR_MTRR4kBase + 8:
@@ -433,6 +437,9 @@ vmx_wrmsr(struct vmx *vmx, int vcpuid, u_int num, uint64_t val, bool *retu)
 	error = 0;
 
 	switch (num) {
+	case MSR_MCG_CAP:
+	case MSR_MCG_STATUS:
+		break;		/* ignore writes */
 	case MSR_MTRRcap:
 		vm_inject_gp(vmx->vm, vcpuid);
 		break;
diff --git a/sys/amd64/vmm/x86.c b/sys/amd64/vmm/x86.c
index 45e08b5..0ddb93c 100644
--- a/sys/amd64/vmm/x86.c
+++ b/sys/amd64/vmm/x86.c
@@ -285,17 +285,20 @@ x86_emulate_cpuid(struct vm *vm, int vcpu_id,
 			 * Hide thermal monitoring
 			 */
 			regs[3] &= ~(CPUID_ACPI | CPUID_TM);
-			
+
 			/*
-			 * Machine check handling is done in the host.
+			 * Hide the debug store capability.
 			 */
-			regs[3] &= ~(CPUID_MCA | CPUID_MCE);
-
-                        /*
-                        * Hide the debug store capability.
-                        */
 			regs[3] &= ~CPUID_DS;
 
+			/*
+			 * Advertise the Machine Check and MTRR capability.
+			 *
+			 * Some guest OSes (e.g. Windows) will not boot if
+			 * these features are absent.
+			 */
+			regs[3] |= (CPUID_MCA | CPUID_MCE | CPUID_MTRR);
+
 			logical_cpus = threads_per_core * cores_per_package;
 			regs[1] &= ~CPUID_HTT_CORES;
 			regs[1] |= (logical_cpus & 0xff) << 16;