KVM: x86 emulator: make (get|set)_dr() callback return error if it fails

Make (get|set)_dr() callback return error if it fails instead of
injecting exception behind emulator's back.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 45 insertions, 29 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 061f7d37c9f7..d5979ecc2521 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3151,9 +3151,14 @@ twobyte_insn:
                         goto done;
                 }
 
-                ops->set_dr(c->modrm_reg,c->regs[c->modrm_rm] &
-                            ((ctxt->mode == X86EMUL_MODE_PROT64) ? ~0ULL : ~0U),
-                        ctxt->vcpu);
+                if (ops->set_dr(c->modrm_reg, c->regs[c->modrm_rm] &
+                                ((ctxt->mode == X86EMUL_MODE_PROT64) ?
+                                 ~0ULL : ~0U), ctxt->vcpu) < 0) {
+                        /* #UD condition is already handled by the code above */
+                        kvm_inject_gp(ctxt->vcpu, 0);
+                        goto done;
+                }
+
                 c->dst.type = OP_NONE;  /* no writeback */
                 break;
         case 0x30:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 64c6e7a31411..44a546b136fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -573,7 +573,7 @@ unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_get_cr8);
 
-int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
+static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 {
         switch (dr) {
         case 0 ... 3:
@@ -582,29 +582,21 @@ int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
                         vcpu->arch.eff_db[dr] = val;
                 break;
         case 4:
-                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
-                        kvm_queue_exception(vcpu, UD_VECTOR);
-                        return 1;
-                }
+                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE))
+                        return 1; /* #UD */
                 /* fall through */
         case 6:
-                if (val & 0xffffffff00000000ULL) {
-                        kvm_inject_gp(vcpu, 0);
-                        return 1;
-                }
+                if (val & 0xffffffff00000000ULL)
+                        return -1; /* #GP */
                 vcpu->arch.dr6 = (val & DR6_VOLATILE) | DR6_FIXED_1;
                 break;
         case 5:
-                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
-                        kvm_queue_exception(vcpu, UD_VECTOR);
-                        return 1;
-                }
+                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE))
+                        return 1; /* #UD */
                 /* fall through */
         default: /* 7 */
-                if (val & 0xffffffff00000000ULL) {
-                        kvm_inject_gp(vcpu, 0);
-                        return 1;
-                }
+                if (val & 0xffffffff00000000ULL)
+                        return -1; /* #GP */
                 vcpu->arch.dr7 = (val & DR7_VOLATILE) | DR7_FIXED_1;
                 if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) {
                         kvm_x86_ops->set_dr7(vcpu, vcpu->arch.dr7);
@@ -615,28 +607,37 @@ int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 
         return 0;
 }
+
+int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
+{
+        int res;
+
+        res = __kvm_set_dr(vcpu, dr, val);
+        if (res > 0)
+                kvm_queue_exception(vcpu, UD_VECTOR);
+        else if (res < 0)
+                kvm_inject_gp(vcpu, 0);
+
+        return res;
+}
 EXPORT_SYMBOL_GPL(kvm_set_dr);
 
-int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
+static int _kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 {
         switch (dr) {
         case 0 ... 3:
                 *val = vcpu->arch.db[dr];
                 break;
         case 4:
-                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
-                        kvm_queue_exception(vcpu, UD_VECTOR);
+                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE))
                         return 1;
-                }
                 /* fall through */
         case 6:
                 *val = vcpu->arch.dr6;
                 break;
         case 5:
-                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE)) {
-                        kvm_queue_exception(vcpu, UD_VECTOR);
+                if (kvm_read_cr4_bits(vcpu, X86_CR4_DE))
                         return 1;
-                }
                 /* fall through */
         default: /* 7 */
                 *val = vcpu->arch.dr7;
@@ -645,6 +646,15 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 
         return 0;
 }
+
+int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
+{
+        if (_kvm_get_dr(vcpu, dr, val)) {
+                kvm_queue_exception(vcpu, UD_VECTOR);
+                return 1;
+        }
+        return 0;
+}
 EXPORT_SYMBOL_GPL(kvm_get_dr);
 
 static inline u32 bit(int bitno)
@@ -3619,12 +3629,13 @@ int emulate_clts(struct kvm_vcpu *vcpu)
 
 int emulator_get_dr(int dr, unsigned long *dest, struct kvm_vcpu *vcpu)
 {
-        return kvm_get_dr(vcpu, dr, dest);
+        return _kvm_get_dr(vcpu, dr, dest);
 }
 
 int emulator_set_dr(int dr, unsigned long value, struct kvm_vcpu *vcpu)
 {
-        return kvm_set_dr(vcpu, dr, value);
+
+        return __kvm_set_dr(vcpu, dr, value);
 }
 
 void kvm_report_emulation_failure(struct kvm_vcpu *vcpu, const char *context)