Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756993Ab3JIJDp (ORCPT ); Wed, 9 Oct 2013 05:03:45 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:59051 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751769Ab3JIJDn (ORCPT ); Wed, 9 Oct 2013 05:03:43 -0400 From: Raghavendra K T To: , , , , , Cc: , , , , , Steven Rostedt , Raghavendra K T Subject: [PATCH] kvm fix: Enable pvspinlock after jump_label_init() to avoid VM hang Date: Wed, 9 Oct 2013 14:33:21 +0530 Message-Id: <1381309401-23663-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: References: X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100909-5806-0000-0000-000023006210 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2169 Lines: 59 We use jump label to enable pv-spinlock. With the changes in (442e0973e927 Merge branch 'x86/jumplabel'), the jump label behaviour has changed that would result in evntual hang of the VM since we would end up in a situation where slowpath locks would halt the vcpus but we will not be able to wakeup the vcpu by lock releaser using unlock kick. Similar problem in Xen and more detailed description is available in a945928ea270 (xen: Do not enable spinlocks before jump_label_init() has executed) This patch splits kvm_spinlock_init to separate jump label changes with pvops patching and also make jump label enabling after jump_label_init(). Signed-off-by: Raghavendra K T --- Thanks to Andrew Theurer who reported weird behaviour of pvspinlock in 3.12-rc that led to my git bisection and investigation and Konrad for his jump label findings for Xen. arch/x86/kernel/kvm.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 697b93a..a0e2a8a 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -775,11 +775,22 @@ void __init kvm_spinlock_init(void) if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) return; - printk(KERN_INFO "KVM setup paravirtual spinlock\n"); + pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); + pv_lock_ops.unlock_kick = kvm_unlock_kick; +} + +static __init int kvm_spinlock_init_jump(void) +{ + if (!kvm_para_available()) + return 0; + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) + return 0; static_key_slow_inc(¶virt_ticketlocks_enabled); + printk(KERN_INFO "KVM setup paravirtual spinlock\n"); - pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); - pv_lock_ops.unlock_kick = kvm_unlock_kick; + return 0; } +early_initcall(kvm_spinlock_init_jump); + #endif /* CONFIG_PARAVIRT_SPINLOCKS */ -- 1.7.11.7 -- 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/