KVM: x86: Add debug register saving and restoring

Make use of the new KVM_GET/SET_DEBUGREGS to save/restore the x86 debug
registers.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

kvm-all.c

@@ -64,6 +64,7 @@ struct KVMState
     int migration_log;
     int vcpu_events;
     int robust_singlestep;
+    int debugregs;
 #ifdef KVM_CAP_SET_GUEST_DEBUG
     struct kvm_sw_breakpoint_head kvm_sw_breakpoints;
 #endif
@@ -664,6 +665,11 @@ int kvm_init(int smp_cpus)
         kvm_check_extension(s, KVM_CAP_X86_ROBUST_SINGLESTEP);
 #endif
 
+    s->debugregs = 0;
+#ifdef KVM_CAP_DEBUGREGS
+    s->debugregs = kvm_check_extension(s, KVM_CAP_DEBUGREGS);
+#endif
+
     ret = kvm_arch_init(s, smp_cpus);
     if (ret < 0)
         goto err;
@@ -939,6 +945,11 @@ int kvm_has_robust_singlestep(void)
     return kvm_state->robust_singlestep;
 }
 
+int kvm_has_debugregs(void)
+{
+    return kvm_state->debugregs;
+}
+
 void kvm_setup_guest_memory(void *start, size_t size)
 {
     if (!kvm_has_sync_mmu()) {

kvm.h

@@ -40,6 +40,7 @@ int kvm_init(int smp_cpus);
 int kvm_has_sync_mmu(void);
 int kvm_has_vcpu_events(void);
 int kvm_has_robust_singlestep(void);
+int kvm_has_debugregs(void);
 
 #ifdef NEED_CPU_H
 int kvm_init_vcpu(CPUState *env);

target-i386/kvm.c

@@ -874,6 +874,53 @@ static int kvm_guest_debug_workarounds(CPUState *env)
     return ret;
 }
 
+static int kvm_put_debugregs(CPUState *env)
+{
+#ifdef KVM_CAP_DEBUGREGS
+    struct kvm_debugregs dbgregs;
+    int i;
+
+    if (!kvm_has_debugregs()) {
+        return 0;
+    }
+
+    for (i = 0; i < 4; i++) {
+        dbgregs.db[i] = env->dr[i];
+    }
+    dbgregs.dr6 = env->dr[6];
+    dbgregs.dr7 = env->dr[7];
+    dbgregs.flags = 0;
+
+    return kvm_vcpu_ioctl(env, KVM_SET_DEBUGREGS, &dbgregs);
+#else
+    return 0;
+#endif
+}
+
+static int kvm_get_debugregs(CPUState *env)
+{
+#ifdef KVM_CAP_DEBUGREGS
+    struct kvm_debugregs dbgregs;
+    int i, ret;
+
+    if (!kvm_has_debugregs()) {
+        return 0;
+    }
+
+    ret = kvm_vcpu_ioctl(env, KVM_GET_DEBUGREGS, &dbgregs);
+    if (ret < 0) {
+       return ret;
+    }
+    for (i = 0; i < 4; i++) {
+        env->dr[i] = dbgregs.db[i];
+    }
+    env->dr[4] = env->dr[6] = dbgregs.dr6;
+    env->dr[5] = env->dr[7] = dbgregs.dr7;
+#endif
+
+    return 0;
+}
+
 int kvm_arch_put_registers(CPUState *env, int level)
 {
     int ret;
@@ -909,6 +956,10 @@ int kvm_arch_put_registers(CPUState *env, int level)
     if (ret < 0)
         return ret;
 
+    ret = kvm_put_debugregs(env);
+    if (ret < 0)
+        return ret;
+
     return 0;
 }
 
@@ -940,6 +991,10 @@ int kvm_arch_get_registers(CPUState *env)
     if (ret < 0)
         return ret;
 
+    ret = kvm_get_debugregs(env);
+    if (ret < 0)
+        return ret;
+
     return 0;
 }