[v2,17/24] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD

Commit Message

Jan Kiszka Feb. 1, 2011, 9:15 p.m. UTC

None

Patch

diff --git a/configure b/configure
index 4673bf0..368ca8a 100755
--- a/configure
+++ b/configure
@@ -2056,6 +2056,12 @@  EOF
 
 if compile_prog "" "" ; then
   signalfd=yes
+elif test "$kvm" = "yes" -a "$io_thread" != "yes"; then
+  echo
+  echo "ERROR: Host kernel lacks signalfd() support,"
+  echo "but KVM depends on it when the IO thread is disabled."
+  echo
+  exit 1
 fi
 
 # check if eventfd is supported
diff --git a/cpus.c b/cpus.c
index 359361f..18caf47 100644
--- a/cpus.c
+++ b/cpus.c
@@ -327,6 +327,12 @@  static void qemu_kvm_eat_signals(CPUState *env)
             exit(1);
         }
     } while (sigismember(&chkset, SIG_IPI) || sigismember(&chkset, SIGBUS));
+
+#ifndef CONFIG_IOTHREAD
+    if (sigismember(&chkset, SIGIO) || sigismember(&chkset, SIGALRM)) {
+        qemu_notify_event();
+    }
+#endif
 }
 
 #else /* _WIN32 */
@@ -376,11 +382,15 @@  static void qemu_kvm_init_cpu_signals(CPUState *env)
 
     sigemptyset(&set);
     sigaddset(&set, SIG_IPI);
+    sigaddset(&set, SIGIO);
+    sigaddset(&set, SIGALRM);
     pthread_sigmask(SIG_BLOCK, &set, NULL);
 
     pthread_sigmask(SIG_BLOCK, NULL, &set);
     sigdelset(&set, SIG_IPI);
     sigdelset(&set, SIGBUS);
+    sigdelset(&set, SIGIO);
+    sigdelset(&set, SIGALRM);
     r = kvm_set_signal_mask(env, &set);
     if (r) {
         fprintf(stderr, "kvm_set_signal_mask: %s\n", strerror(-r));
@@ -389,13 +399,32 @@  static void qemu_kvm_init_cpu_signals(CPUState *env)
 #endif
 }
 
+#ifndef _WIN32
+static sigset_t block_synchronous_signals(void)
+{
+    sigset_t set;
+
+    sigemptyset(&set);
+    if (kvm_enabled()) {
+        /*
+         * We need to process timer signals synchronously to avoid a race
+         * between exit_request check and KVM vcpu entry.
+         */
+        sigaddset(&set, SIGIO);
+        sigaddset(&set, SIGALRM);
+    }
+
+    return set;
+}
+#endif
+
 int qemu_init_main_loop(void)
 {
 #ifndef _WIN32
     sigset_t blocked_signals;
     int ret;
 
-    sigemptyset(&blocked_signals);
+    blocked_signals = block_synchronous_signals();
 
     ret = qemu_signalfd_init(blocked_signals);
     if (ret) {