From patchwork Mon Sep 30 12:44:36 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhenzhong Duan X-Patchwork-Id: 11168675 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id ED22816B1 for ; Tue, 1 Oct 2019 12:43:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C298821A4A for ; Tue, 1 Oct 2019 12:43:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="HyCQuURl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387896AbfJAMnw (ORCPT ); Tue, 1 Oct 2019 08:43:52 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:36558 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732701AbfJAMnw (ORCPT ); Tue, 1 Oct 2019 08:43:52 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x91CNrDw145664; Tue, 1 Oct 2019 12:42:02 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2019-08-05; bh=ZJU7loQMKeSoP/RlUzFVBDI3b7KBQRKdPz3cE8BrKSw=; b=HyCQuURlBEJp1HNn+K0A6naF6KTrnqsDw2P3Gl/qrFMjZ1/sY6+ApajqNZF7NusOL5oK J/X1wrOozJNLLagKbKtvPVAc9LVXcyfVIzzpnjRmJf0aTyKpFjT4Fd9VNU4NWGueus32 YaHEqGCHQIaoGfi7aHwttWUNiCWx8yJAXI/qqSrxfOOD/MVTfvhBmhcTvsNAfQWKdydQ MZkiqrHfqGjh5VAFbWteHlw98rr2HTmW7t3zr3SQHzB66yGmkdgX+vleWSbsh24XdsAh c1CHfFlYIRZJ0MN0uC8zndPsBUdhEWgmqBXu7N9FBdzJiTLO4IzVDOuj0cLFP/gJn1vG cw== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 2v9yfq5gpq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 01 Oct 2019 12:42:02 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x91COQJQ039749; Tue, 1 Oct 2019 12:40:01 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 2vbqd0suuq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 01 Oct 2019 12:40:01 +0000 Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x91Cdxo9005795; Tue, 1 Oct 2019 12:39:59 GMT Received: from z2.cn.oracle.com (/10.182.71.205) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 01 Oct 2019 05:39:58 -0700 From: Zhenzhong Duan To: linux-kernel@vger.kernel.org Cc: vkuznets@redhat.com, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, Zhenzhong Duan , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Paolo Bonzini , Radim Krcmar , Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel , Peter Zijlstra , Will Deacon Subject: [PATCH v3 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks Date: Mon, 30 Sep 2019 20:44:36 +0800 Message-Id: <1569847479-13201-2-git-send-email-zhenzhong.duan@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1569847479-13201-1-git-send-email-zhenzhong.duan@oracle.com> References: <1569847479-13201-1-git-send-email-zhenzhong.duan@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9396 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010114 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9396 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010114 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org There are cases where a guest tries to switch spinlocks to bare metal behavior (e.g. by setting "xen_nopvspin" on XEN platform and "hv_nopvspin" on HYPER_V). That feature is missed on KVM, add a new parameter "nopvspin" to disable PV spinlocks for KVM guest. This new parameter is also used to replace "xen_nopvspin" and "hv_nopvspin". The global variable pvspin isn't defined as __initdata as it's used at runtime by XEN guest. Signed-off-by: Zhenzhong Duan Cc: Jonathan Corbet Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Paolo Bonzini Cc: Radim Krcmar Cc: Sean Christopherson Cc: Vitaly Kuznetsov Cc: Wanpeng Li Cc: Jim Mattson Cc: Joerg Roedel Cc: Peter Zijlstra Cc: Will Deacon --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/x86/include/asm/qspinlock.h | 1 + arch/x86/kernel/kvm.c | 7 +++++++ kernel/locking/qspinlock.c | 7 +++++++ 4 files changed, 19 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c7ac2f3..4b956d8 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5330,6 +5330,10 @@ as generic guest with no PV drivers. Currently support XEN HVM, KVM, HYPER_V and VMWARE guest. + nopvspin [X86,KVM] Disables the qspinlock slow path + using PV optimizations which allow the hypervisor to + 'idle' the guest on lock contention. + xirc2ps_cs= [NET,PCMCIA] Format: ,,,,,[,[,[,]]] diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index 444d6fd..34a4484 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -32,6 +32,7 @@ static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lo extern void __pv_init_lock_hash(void); extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val); extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock); +extern bool pvspin; #define queued_spin_unlock queued_spin_unlock /** diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index e820568..a4f108d 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -842,6 +842,13 @@ void __init kvm_spinlock_init(void) if (num_possible_cpus() == 1) return; + if (!pvspin) { + pr_info("PV spinlocks disabled\n"); + static_branch_disable(&virt_spin_lock_key); + return; + } + pr_info("PV spinlocks enabled\n"); + __pv_init_lock_hash(); pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath; pv_ops.lock.queued_spin_unlock = diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 2473f10..945b510 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -580,4 +580,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) #include "qspinlock_paravirt.h" #include "qspinlock.c" +bool pvspin = true; +static __init int parse_nopvspin(char *arg) +{ + pvspin = false; + return 0; +} +early_param("nopvspin", parse_nopvspin); #endif