Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753270Ab3F1S4D (ORCPT ); Fri, 28 Jun 2013 14:56:03 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:41771 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752652Ab3F1Sz7 (ORCPT ); Fri, 28 Jun 2013 14:55:59 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Marcelo Tosatti , Kamal Mostafa Subject: [PATCH 105/105] KVM: x86: fix deadlock in clock-in-progress request handling Date: Fri, 28 Jun 2013 11:52:07 -0700 Message-Id: <1372445527-24414-106-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1372445527-24414-1-git-send-email-kamal@canonical.com> References: <1372445527-24414-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2540 Lines: 81 3.8.13.4 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Marcelo Tosatti commit c09664bb44184b3846e8c5254db4eae4b932682a upstream. There is a deadlock in pvclock handling: cpu0: cpu1: kvm_gen_update_masterclock() kvm_guest_time_update() spin_lock(pvclock_gtod_sync_lock) local_irq_save(flags) spin_lock(pvclock_gtod_sync_lock) kvm_make_mclock_inprogress_request(kvm) make_all_cpus_request() smp_call_function_many() Now if smp_call_function_many() called by cpu0 tries to call function on cpu1 there will be a deadlock. Fix by moving pvclock_gtod_sync_lock protected section outside irq disabled section. Analyzed by Gleb Natapov Acked-by: Gleb Natapov Reported-and-Tested-by: Yongjie Ren Signed-off-by: Marcelo Tosatti Signed-off-by: Kamal Mostafa --- arch/x86/kvm/x86.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ff74a2c..6e2af7b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1416,15 +1416,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) kernel_ns = 0; host_tsc = 0; - /* Keep irq disabled to prevent changes to the clock */ - local_irq_save(flags); - this_tsc_khz = __get_cpu_var(cpu_tsc_khz); - if (unlikely(this_tsc_khz == 0)) { - local_irq_restore(flags); - kvm_make_request(KVM_REQ_CLOCK_UPDATE, v); - return 1; - } - /* * If the host uses TSC clock, then passthrough TSC as stable * to the guest. @@ -1436,6 +1427,15 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) kernel_ns = ka->master_kernel_ns; } spin_unlock(&ka->pvclock_gtod_sync_lock); + + /* Keep irq disabled to prevent changes to the clock */ + local_irq_save(flags); + this_tsc_khz = __get_cpu_var(cpu_tsc_khz); + if (unlikely(this_tsc_khz == 0)) { + local_irq_restore(flags); + kvm_make_request(KVM_REQ_CLOCK_UPDATE, v); + return 1; + } if (!use_master_clock) { host_tsc = native_read_tsc(); kernel_ns = get_kernel_ns(); -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/