[PATCH 09/19] KVM: x86: Add #CP support in guest exception classification.

[Yang Weijiang]

Add handling for Control Protection (#CP) exceptions, vector 21, used
and introduced by Intel's Control-Flow Enforcement Technology (CET).
relevant CET violation case.  See Intel's SDM for details.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Message-Id: <20210203113421.5759-5-weijiang.yang@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/include/uapi/asm/kvm.h |  1 +
 arch/x86/kvm/vmx/nested.c       |  2 +-
 arch/x86/kvm/x86.c              | 10 +++++++---
 arch/x86/kvm/x86.h              | 13 ++++++++++---
 4 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 50a4e787d5e6..69146e7436af 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -32,6 +32,7 @@
 #define MC_VECTOR 18
 #define XM_VECTOR 19
 #define VE_VECTOR 20
+#define CP_VECTOR 21
 
 /* Select x86 specific features in <linux/kvm.h> */
 #define __KVM_HAVE_PIT
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 7d8cd0ebcc75..01fe23c6fa49 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2819,7 +2819,7 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
 		/* VM-entry interruption-info field: deliver error code */
 		should_have_error_code =
 			intr_type == INTR_TYPE_HARD_EXCEPTION && prot_mode &&
-			x86_exception_has_error_code(vector);
+			x86_exception_has_error_code(vcpu, vector);
 		if (CC(has_error_code != should_have_error_code))
 			return -EINVAL;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 506454e17afc..40749e47cda7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -511,11 +511,15 @@ EXPORT_SYMBOL_GPL(kvm_spurious_fault);
 #define EXCPT_CONTRIBUTORY	1
 #define EXCPT_PF		2
 
-static int exception_class(int vector)
+static int exception_class(struct kvm_vcpu *vcpu, int vector)
 {
 	switch (vector) {
 	case PF_VECTOR:
 		return EXCPT_PF;
+	case CP_VECTOR:
+		if (vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET)
+			return EXCPT_BENIGN;
+		return EXCPT_CONTRIBUTORY;
 	case DE_VECTOR:
 	case TS_VECTOR:
 	case NP_VECTOR:
@@ -659,8 +663,8 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
 		kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
 		return;
 	}
-	class1 = exception_class(prev_nr);
-	class2 = exception_class(nr);
+	class1 = exception_class(vcpu, prev_nr);
+	class2 = exception_class(vcpu, nr);
 	if ((class1 == EXCPT_CONTRIBUTORY && class2 == EXCPT_CONTRIBUTORY)
 		|| (class1 == EXCPT_PF && class2 != EXCPT_BENIGN)) {
 		/*
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 501b884b8cc4..b9b1fff6d97a 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -148,13 +148,20 @@ static inline bool is_64_bit_hypercall(struct kvm_vcpu *vcpu)
 	return vcpu->arch.guest_state_protected || is_64_bit_mode(vcpu);
 }
 
-static inline bool x86_exception_has_error_code(unsigned int vector)
+static inline bool x86_exception_has_error_code(struct kvm_vcpu *vcpu,
+						unsigned int vector)
 {
 	static u32 exception_has_error_code = BIT(DF_VECTOR) | BIT(TS_VECTOR) |
 			BIT(NP_VECTOR) | BIT(SS_VECTOR) | BIT(GP_VECTOR) |
-			BIT(PF_VECTOR) | BIT(AC_VECTOR);
+			BIT(PF_VECTOR) | BIT(AC_VECTOR) | BIT(CP_VECTOR);
 
-	return (1U << vector) & exception_has_error_code;
+	if (!((1U << vector) & exception_has_error_code))
+		return false;
+
+	if (vector == CP_VECTOR)
+		return !(vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET);
+
+	return true;
 }
 
 static inline bool mmu_is_nested(struct kvm_vcpu *vcpu)
-- 
2.27.0