[PATCH v2] KVM: nVMX: Fix read/write to MSR_IA32_FEATURE_CONTROL

[Arthur Chunqi Li <yzt356@gmail.com>]

Fix read/write to IA32_FEATURE_CONTROL MSR in nested environment.

This patch simulate this MSR in nested_vmx and the default value is
0x0. BIOS should set it to 0x5 before VMXON. After setting the lock
bit, write to it will cause #GP(0).

Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>
---
 arch/x86/kvm/vmx.c |   25 +++++++++++++++++++++----
 arch/x86/kvm/x86.c |    3 ++-
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 260a919..5e3d44e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -373,6 +373,7 @@ struct nested_vmx {
 	 * we must keep them pinned while L2 runs.
 	 */
 	struct page *apic_access_page;
+	u64 msr_ia32_feature_control;
 };
 
 #define POSTED_INTR_ON  0
@@ -2277,8 +2278,11 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
 
 	switch (msr_index) {
 	case MSR_IA32_FEATURE_CONTROL:
-		*pdata = 0;
-		break;
+		if (nested_vmx_allowed(vcpu)){
+			*pdata = to_vmx(vcpu)->nested.msr_ia32_feature_control;
+			break;
+		}
+		return 0;
 	case MSR_IA32_VMX_BASIC:
 		/*
 		 * This MSR reports some information about VMX support. We
@@ -2356,9 +2360,13 @@ static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 	if (!nested_vmx_allowed(vcpu))
 		return 0;
 
-	if (msr_index == MSR_IA32_FEATURE_CONTROL)
-		/* TODO: the right thing. */
+	if (msr_index == MSR_IA32_FEATURE_CONTROL){
+		if (to_vmx(vcpu)->nested.msr_ia32_feature_control
+				& FEATURE_CONTROL_LOCKED)
+			return 0;
+		to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
 		return 1;
+	}
 	/*
 	 * No need to treat VMX capability MSRs specially: If we don't handle
 	 * them, handle_wrmsr will #GP(0), which is correct (they are readonly)
@@ -5595,6 +5603,15 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
 		skip_emulated_instruction(vcpu);
 		return 1;
 	}
+
+#define VMXON_NEEDED_FEATURES \
+	  (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX)
+	if ((vmx->nested.msr_ia32_feature_control & VMXON_NEEDED_FEATURES)
+			!= VMXON_NEEDED_FEATURES) {
+		kvm_inject_gp(vcpu, 0);
+		return 1;
+	}
+
 	if (enable_shadow_vmcs) {
 		shadow_vmcs = alloc_vmcs();
 		if (!shadow_vmcs)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e8ba99c..2d4eb8e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -850,7 +850,8 @@ static u32 msrs_to_save[] = {
 #ifdef CONFIG_X86_64
 	MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
 #endif
-	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
+	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
+	MSR_IA32_FEATURE_CONTROL
 };
 
 static unsigned num_msrs_to_save;
-- 
1.7.9.5