From patchwork Sun Jun 15 12:47:05 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 4354481 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 8F5259F314 for ; Sun, 15 Jun 2014 13:16:55 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A2EC3201FA for ; Sun, 15 Jun 2014 13:16:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3FD9201F4 for ; Sun, 15 Jun 2014 13:16:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936AbaFONQg (ORCPT ); Sun, 15 Jun 2014 09:16:36 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:60395 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbaFONMD (ORCPT ); Sun, 15 Jun 2014 09:12:03 -0400 Received: from dhcp-077-248-225-117.chello.nl ([77.248.225.117] helo=laptop) by bombadil.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1WwADk-000453-1l; Sun, 15 Jun 2014 13:11:40 +0000 Received: by laptop (Postfix, from userid 0) id 9797E107F074C; Sun, 15 Jun 2014 15:11:36 +0200 (CEST) Message-Id: <20140615130153.940699466@chello.nl> User-Agent: quilt/0.61-1 Date: Sun, 15 Jun 2014 14:47:05 +0200 From: Peter Zijlstra To: Waiman.Long@hp.com, tglx@linutronix.de, mingo@kernel.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, paolo.bonzini@gmail.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, paulmck@linux.vnet.ibm.com, riel@redhat.com, torvalds@linux-foundation.org, raghavendra.kt@linux.vnet.ibm.com, david.vrabel@citrix.com, oleg@redhat.com, gleb@redhat.com, scott.norton@hp.com, chegu_vinod@hp.com, Peter Zijlstra Subject: [PATCH 08/11] qspinlock: Revert to test-and-set on hypervisors References: <20140615124657.264658593@chello.nl> MIME-Version: 1.0 Content-Disposition: inline; filename=peterz-qspinlock-test-and-set.patch Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When we detect a hypervisor (!paravirt, see later patches), revert to a simple test-and-set lock to avoid the horrors of queue preemption. Signed-off-by: Peter Zijlstra --- arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ include/asm-generic/qspinlock.h | 7 +++++++ kernel/locking/qspinlock.c | 3 +++ 3 files changed, 24 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -1,6 +1,7 @@ #ifndef _ASM_X86_QSPINLOCK_H #define _ASM_X86_QSPINLOCK_H +#include #include #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) @@ -20,6 +21,19 @@ static inline void queue_spin_unlock(str #endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ +#define virt_queue_spin_lock virt_queue_spin_lock + +static inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + return false; + + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) + cpu_relax(); + + return true; +} + #include #endif /* _ASM_X86_QSPINLOCK_H */ --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -98,6 +98,13 @@ static __always_inline void queue_spin_u } #endif +#ifndef virt_queue_spin_lock +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -247,6 +247,9 @@ void queue_spin_lock_slowpath(struct qsp BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (virt_queue_spin_lock(lock)) + return; + /* * wait for in-progress pending->locked hand-overs *