[1/4] KVM: Rework of guest debug state writing

Commit Message

Jan Kiszka March 1, 2010, 6:10 p.m. UTC

None

Patch

diff --git a/kvm-all.c b/kvm-all.c
index 1a02076..2f7e33a 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -65,6 +65,7 @@  struct KVMState
     int broken_set_mem_region;
     int migration_log;
     int vcpu_events;
+    int robust_singlestep;
 #ifdef KVM_CAP_SET_GUEST_DEBUG
     struct kvm_sw_breakpoint_head kvm_sw_breakpoints;
 #endif
@@ -659,6 +660,12 @@  int kvm_init(int smp_cpus)
     s->vcpu_events = kvm_check_extension(s, KVM_CAP_VCPU_EVENTS);
 #endif
 
+    s->robust_singlestep = 0;
+#ifdef KVM_CAP_X86_ROBUST_SINGLESTEP
+    s->robust_singlestep =
+        kvm_check_extension(s, KVM_CAP_X86_ROBUST_SINGLESTEP);
+#endif
+
     ret = kvm_arch_init(s, smp_cpus);
     if (ret < 0)
         goto err;
@@ -917,6 +924,11 @@  int kvm_has_vcpu_events(void)
     return kvm_state->vcpu_events;
 }
 
+int kvm_has_robust_singlestep(void)
+{
+    return kvm_state->robust_singlestep;
+}
+
 void kvm_setup_guest_memory(void *start, size_t size)
 {
     if (!kvm_has_sync_mmu()) {
@@ -974,10 +986,6 @@  static void kvm_invoke_set_guest_debug(void *data)
     struct kvm_set_guest_debug_data *dbg_data = data;
     CPUState *env = dbg_data->env;
 
-    if (env->kvm_vcpu_dirty) {
-        kvm_arch_put_registers(env);
-        env->kvm_vcpu_dirty = 0;
-    }
     dbg_data->err = kvm_vcpu_ioctl(env, KVM_SET_GUEST_DEBUG, &dbg_data->dbg);
 }
 
@@ -985,12 +993,12 @@  int kvm_update_guest_debug(CPUState *env, unsigned long reinject_trap)
 {
     struct kvm_set_guest_debug_data data;
 
-    data.dbg.control = 0;
-    if (env->singlestep_enabled)
-        data.dbg.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
+    data.dbg.control = reinject_trap;
 
+    if (env->singlestep_enabled) {
+        data.dbg.control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
+    }
     kvm_arch_update_guest_debug(env, &data.dbg);
-    data.dbg.control |= reinject_trap;
     data.env = env;
 
     on_vcpu(env, kvm_invoke_set_guest_debug, &data);
diff --git a/kvm.h b/kvm.h
index a74dfcb..a602e45 100644
--- a/kvm.h
+++ b/kvm.h
@@ -40,6 +40,7 @@  int kvm_log_stop(target_phys_addr_t phys_addr, ram_addr_t size);
 
 int kvm_has_sync_mmu(void);
 int kvm_has_vcpu_events(void);
+int kvm_has_robust_singlestep(void);
 
 void kvm_setup_guest_memory(void *start, size_t size);
 
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 6b741ba..2365ca3 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -851,6 +851,37 @@  static int kvm_get_vcpu_events(CPUState *env)
     return 0;
 }
 
+static int kvm_guest_debug_workarounds(CPUState *env)
+{
+    int ret = 0;
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+    unsigned long reinject_trap = 0;
+
+    if (!kvm_has_vcpu_events()) {
+        if (env->exception_injected == 1) {
+            reinject_trap = KVM_GUESTDBG_INJECT_DB;
+        } else if (env->exception_injected == 3) {
+            reinject_trap = KVM_GUESTDBG_INJECT_BP;
+        }
+        env->exception_injected = -1;
+    }
+
+    /*
+     * Kernels before KVM_CAP_X86_ROBUST_SINGLESTEP overwrote flags.TF
+     * injected via SET_GUEST_DEBUG while updating GP regs. Work around this
+     * by updating the debug state once again if single-stepping is on.
+     * Another reason to call kvm_update_guest_debug here is a pending debug
+     * trap raise by the guest. On kernels without SET_VCPU_EVENTS we have to
+     * reinject them via SET_GUEST_DEBUG.
+     */
+    if (reinject_trap ||
+        (!kvm_has_robust_singlestep() && env->singlestep_enabled)) {
+        ret = kvm_update_guest_debug(env, reinject_trap);
+    }
+#endif /* KVM_CAP_SET_GUEST_DEBUG */
+    return ret;
+}
+
 int kvm_arch_put_registers(CPUState *env)
 {
     int ret;
@@ -879,6 +910,11 @@  int kvm_arch_put_registers(CPUState *env)
     if (ret < 0)
         return ret;
 
+    /* must be last */
+    ret = kvm_guest_debug_workarounds(env);
+    if (ret < 0)
+        return ret;
+
     return 0;
 }
 
@@ -1122,10 +1158,13 @@  int kvm_arch_debug(struct kvm_debug_exit_arch *arch_info)
     } else if (kvm_find_sw_breakpoint(cpu_single_env, arch_info->pc))
         handle = 1;
 
-    if (!handle)
-        kvm_update_guest_debug(cpu_single_env,
-                        (arch_info->exception == 1) ?
-                        KVM_GUESTDBG_INJECT_DB : KVM_GUESTDBG_INJECT_BP);
+    if (!handle) {
+        cpu_synchronize_state(cpu_single_env);
+        assert(cpu_single_env->exception_injected == -1);
+
+        cpu_single_env->exception_injected = arch_info->exception;
+        cpu_single_env->has_error_code = 0;
+    }
 
     return handle;
 }