From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: [PATCH 14/22] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD Date: Thu, 27 Jan 2011 14:09:58 +0100 Message-ID: References: Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org, Stefan Hajnoczi To: Avi Kivity , Marcelo Tosatti Return-path: Received: from david.siemens.de ([192.35.17.14]:19781 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753182Ab1A0NK1 (ORCPT ); Thu, 27 Jan 2011 08:10:27 -0500 In-Reply-To: In-Reply-To: References: Sender: kvm-owner@vger.kernel.org List-ID: Found by Stefan Hajnoczi: There is a race in kvm_cpu_exec between checking for exit_request on vcpu entry and timer signals arriving before KVM starts to catch them. Plug it by blocking both timer related signals also on !CONFIG_IOTHREAD and process those via signalfd. Signed-off-by: Jan Kiszka CC: Stefan Hajnoczi --- cpus.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) diff --git a/cpus.c b/cpus.c index fc3f222..29b1070 100644 --- a/cpus.c +++ b/cpus.c @@ -254,6 +254,10 @@ static void qemu_kvm_init_cpu_signals(CPUState *env) pthread_sigmask(SIG_BLOCK, NULL, &set); sigdelset(&set, SIG_IPI); sigdelset(&set, SIGBUS); +#ifndef CONFIG_IOTHREAD + sigdelset(&set, SIGIO); + sigdelset(&set, SIGALRM); +#endif r = kvm_set_signal_mask(env, &set); if (r) { fprintf(stderr, "kvm_set_signal_mask: %s\n", strerror(-r)); @@ -351,6 +355,12 @@ 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 */ @@ -398,6 +408,14 @@ int qemu_init_main_loop(void) int ret; sigemptyset(&blocked_signals); + if (kvm_enabled()) { + /* + * We need to process timer signals synchronously to avoid a race + * between exit_request check and KVM vcpu entry. + */ + sigaddset(&blocked_signals, SIGIO); + sigaddset(&blocked_signals, SIGALRM); + } ret = qemu_signalfd_init(blocked_signals); if (ret) { -- 1.7.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=49390 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PiRc9-0001SK-SV for qemu-devel@nongnu.org; Thu, 27 Jan 2011 08:10:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PiRc7-0000kw-3W for qemu-devel@nongnu.org; Thu, 27 Jan 2011 08:10:17 -0500 Received: from david.siemens.de ([192.35.17.14]:19701) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PiRc6-0000jc-8E for qemu-devel@nongnu.org; Thu, 27 Jan 2011 08:10:14 -0500 From: Jan Kiszka Date: Thu, 27 Jan 2011 14:09:58 +0100 Message-Id: In-Reply-To: References: In-Reply-To: References: Subject: [Qemu-devel] [PATCH 14/22] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity , Marcelo Tosatti Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Stefan Hajnoczi Found by Stefan Hajnoczi: There is a race in kvm_cpu_exec between checking for exit_request on vcpu entry and timer signals arriving before KVM starts to catch them. Plug it by blocking both timer related signals also on !CONFIG_IOTHREAD and process those via signalfd. Signed-off-by: Jan Kiszka CC: Stefan Hajnoczi --- cpus.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) diff --git a/cpus.c b/cpus.c index fc3f222..29b1070 100644 --- a/cpus.c +++ b/cpus.c @@ -254,6 +254,10 @@ static void qemu_kvm_init_cpu_signals(CPUState *env) pthread_sigmask(SIG_BLOCK, NULL, &set); sigdelset(&set, SIG_IPI); sigdelset(&set, SIGBUS); +#ifndef CONFIG_IOTHREAD + sigdelset(&set, SIGIO); + sigdelset(&set, SIGALRM); +#endif r = kvm_set_signal_mask(env, &set); if (r) { fprintf(stderr, "kvm_set_signal_mask: %s\n", strerror(-r)); @@ -351,6 +355,12 @@ 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 */ @@ -398,6 +408,14 @@ int qemu_init_main_loop(void) int ret; sigemptyset(&blocked_signals); + if (kvm_enabled()) { + /* + * We need to process timer signals synchronously to avoid a race + * between exit_request check and KVM vcpu entry. + */ + sigaddset(&blocked_signals, SIGIO); + sigaddset(&blocked_signals, SIGALRM); + } ret = qemu_signalfd_init(blocked_signals); if (ret) { -- 1.7.1