KVM: VMX: Fix emulation of DR4 and DR5

Make sure DR4 and DR5 are aliased to DR6 and DR7, respectively, if
CR4.DE is not set.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 26 insertions, 9 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9727773f24b7..c7b99e1f8aae 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3039,6 +3039,15 @@ static int handle_cr(struct kvm_vcpu *vcpu)
         return 0;
 }
 
+static int check_dr_alias(struct kvm_vcpu *vcpu)
+{
+        if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
+                kvm_queue_exception(vcpu, UD_VECTOR);
+                return -1;
+        }
+        return 0;
+}
+
 static int handle_dr(struct kvm_vcpu *vcpu)
 {
         unsigned long exit_qualification;
@@ -3081,14 +3090,20 @@ static int handle_dr(struct kvm_vcpu *vcpu)
                 case 0 ... 3:
                         val = vcpu->arch.db[dr];
                         break;
+                case 4:
+                        if (check_dr_alias(vcpu) < 0)
+                                return 1;
+                        /* fall through */
                 case 6:
                         val = vcpu->arch.dr6;
                         break;
-                case 7:
+                case 5:
+                        if (check_dr_alias(vcpu) < 0)
+                                return 1;
+                        /* fall through */
+                default: /* 7 */
                         val = vcpu->arch.dr7;
                         break;
-                default:
-                        val = 0;
                 }
                 kvm_register_write(vcpu, reg, val);
         } else {
@@ -3099,12 +3114,10 @@ static int handle_dr(struct kvm_vcpu *vcpu)
                         if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
                                 vcpu->arch.eff_db[dr] = val;
                         break;
-                case 4 ... 5:
-                        if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
-                                kvm_queue_exception(vcpu, UD_VECTOR);
+                case 4:
+                        if (check_dr_alias(vcpu) < 0)
                                 return 1;
-                        }
-                        break;
+                        /* fall through */
                 case 6:
                         if (val & 0xffffffff00000000ULL) {
                                 kvm_inject_gp(vcpu, 0);
@@ -3112,7 +3125,11 @@ static int handle_dr(struct kvm_vcpu *vcpu)
                         }
                         vcpu->arch.dr6 = (val & DR6_VOLATILE) | DR6_FIXED_1;
                         break;
-                case 7:
+                case 5:
+                        if (check_dr_alias(vcpu) < 0)
+                                return 1;
+                        /* fall through */
+                default: /* 7 */
                         if (val & 0xffffffff00000000ULL) {
                                 kvm_inject_gp(vcpu, 0);
                                 return 1;