From: Marcelo Tosatti <mtosatti@redhat.com> To: Anthony Liguori <aliguori@us.ibm.com> Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Jan Kiszka <jan.kiszka@siemens.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com> Subject: [PATCH 16/23] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD Date: Fri, 4 Feb 2011 13:47:19 -0200 [thread overview] Message-ID: <4a3cf4661e663df87b315d7556b047b0d8b2aa58.1296834446.git.mtosatti@redhat.com> (raw) In-Reply-To: <cover.1296834446.git.mtosatti@redhat.com> From: Jan Kiszka <jan.kiszka@siemens.com> 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. As this fix depends on real signalfd support (otherwise the timer signals only kick the compat helper thread, and the main thread hangs), we need to detect the invalid constellation and abort configure. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> CC: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> --- configure | 6 ++++++ cpus.c | 31 ++++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletions(-) diff --git a/configure b/configure index 598e8e1..a3f5345 100755 --- a/configure +++ b/configure @@ -2057,6 +2057,12 @@ 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) { -- 1.7.2.3
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com> To: Anthony Liguori <aliguori@us.ibm.com> Cc: Jan Kiszka <jan.kiszka@siemens.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 16/23] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD Date: Fri, 4 Feb 2011 13:47:19 -0200 [thread overview] Message-ID: <4a3cf4661e663df87b315d7556b047b0d8b2aa58.1296834446.git.mtosatti@redhat.com> (raw) In-Reply-To: <cover.1296834446.git.mtosatti@redhat.com> From: Jan Kiszka <jan.kiszka@siemens.com> 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. As this fix depends on real signalfd support (otherwise the timer signals only kick the compat helper thread, and the main thread hangs), we need to detect the invalid constellation and abort configure. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> CC: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> --- configure | 6 ++++++ cpus.c | 31 ++++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletions(-) diff --git a/configure b/configure index 598e8e1..a3f5345 100755 --- a/configure +++ b/configure @@ -2057,6 +2057,12 @@ 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) { -- 1.7.2.3
next prev parent reply other threads:[~2011-02-04 15:49 UTC|newest] Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-02-04 15:47 [PATCH 00/23] [PULL] qemu-kvm.git uq/master queue Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 01/23] Prevent abortion on multiple VCPU kicks Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 02/23] Stop current VCPU on synchronous reset requests Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 03/23] Process vmstop requests in IO thread Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 04/23] Trigger exit from cpu_exec_all on pending IO events Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 05/23] Leave inner main_loop faster on pending requests Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 06/23] Flatten the main loop Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 07/23] kvm: Report proper error on GET_VCPU_MMAP_SIZE failures Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 08/23] kvm: Drop redundant kvm_enabled from kvm_cpu_thread_fn Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 09/23] kvm: Handle kvm_init_vcpu errors Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 10/23] kvm: Provide sigbus services arch-independently Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 11/23] Refactor signal setup functions in cpus.c Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 12/23] kvm: Set up signal mask also for !CONFIG_IOTHREAD Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 13/23] kvm: Refactor qemu_kvm_eat_signals Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 14/23] kvm: Call qemu_kvm_eat_signals also under !CONFIG_IOTHREAD Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 15/23] Set up signalfd " Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` Marcelo Tosatti [this message] 2011-02-04 15:47 ` [Qemu-devel] [PATCH 16/23] kvm: Fix race between timer signals and vcpu entry under !IOTHREAD Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 17/23] kvm: Add MCE signal support for !CONFIG_IOTHREAD Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 18/23] Introduce VCPU self-signaling service Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 19/23] kvm: Unconditionally reenter kernel after IO exits Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 20/23] kvm: Remove static return code of kvm_handle_io Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 21/23] kvm: Leave kvm_cpu_exec directly after KVM_EXIT_SHUTDOWN Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 15:47 ` [PATCH 22/23] x86: Fix MCA broadcast parameters for TCG case Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-08 11:39 ` Aurelien Jarno 2011-02-08 11:39 ` Aurelien Jarno 2011-02-08 11:42 ` Jan Kiszka 2011-02-08 11:42 ` Jan Kiszka 2011-02-04 15:47 ` [PATCH 23/23] kvm: make tsc stable over migration and machine start Marcelo Tosatti 2011-02-04 15:47 ` [Qemu-devel] " Marcelo Tosatti 2011-02-04 17:34 ` [Qemu-devel] [PATCH 00/23] [PULL] qemu-kvm.git uq/master queue Anthony Liguori 2011-02-04 17:34 ` Anthony Liguori 2011-02-04 17:52 ` Jan Kiszka 2011-02-04 18:21 ` [PATCH v3 02/23] Stop current VCPU on synchronous reset requests Jan Kiszka 2011-02-04 18:21 ` [Qemu-devel] " Jan Kiszka 2011-02-04 21:22 ` Marcelo Tosatti 2011-02-04 21:22 ` [Qemu-devel] " Marcelo Tosatti
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