KVM: VMX: Fix exceptions of mov to dr

Injecting GP without an error code is a bad idea (causes unhandled guest
exits). Moreover, we must not skip the instruction if we injected an
exception.

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

1 files changed, 8 insertions, 5 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 516084f3c6d8..9727773f24b7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3045,6 +3045,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
         unsigned long val;
         int dr, reg;
 
+        /* Do not handle if the CPL > 0, will trigger GP on re-entry */
         if (!kvm_require_cpl(vcpu, 0))
                 return 1;
         dr = vmcs_readl(GUEST_DR7);
@@ -3099,20 +3100,22 @@ static int handle_dr(struct kvm_vcpu *vcpu)
                                 vcpu->arch.eff_db[dr] = val;
                         break;
                 case 4 ... 5:
-                        if (kvm_read_cr4_bits(vcpu, X86_CR4_DE))
+                        if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
                                 kvm_queue_exception(vcpu, UD_VECTOR);
+                                return 1;
+                        }
                         break;
                 case 6:
                         if (val & 0xffffffff00000000ULL) {
-                                kvm_queue_exception(vcpu, GP_VECTOR);
-                                break;
+                                kvm_inject_gp(vcpu, 0);
+                                return 1;
                         }
                         vcpu->arch.dr6 = (val & DR6_VOLATILE) | DR6_FIXED_1;
                         break;
                 case 7:
                         if (val & 0xffffffff00000000ULL) {
-                                kvm_queue_exception(vcpu, GP_VECTOR);
-                                break;
+                                kvm_inject_gp(vcpu, 0);
+                                return 1;
                         }
                         vcpu->arch.dr7 = (val & DR7_VOLATILE) | DR7_FIXED_1;
                         if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) {