From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D605ECE58C for ; Tue, 8 Oct 2019 02:20:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 121B7206BB for ; Tue, 8 Oct 2019 02:20:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="ieozgDXd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729809AbfJHCUk (ORCPT ); Mon, 7 Oct 2019 22:20:40 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:51272 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729285AbfJHCUk (ORCPT ); Mon, 7 Oct 2019 22:20:40 -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 x982IkdU048775; Tue, 8 Oct 2019 02:18:46 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2019-08-05; bh=I/1ZOG0KQJ1XeouCR4SXL2HIi2M9pjNcEOAgDRDriec=; b=ieozgDXdAP/HFecEbs0rlI3ui4NXJVl3C1Oo0S3R7rKggz/O0GKuzVaLrzWN4MTmIIAC 9/ktb9euli0iXh0BkHGfbQzo4YPqjI1VBmFd4GtNyhpfS57XfGmMTSYYPdcBh7NCYuTL 5YPQioPLpPwuVGggRWeXLtAaNF/0rbltyQgnzbBUt4lv5u/u4V9NaoFEFxd5orNxLAZR +XL3zjwS6Qc6JIoHykCn7/W9glDF4faVnO9nqJocaTUjUToU6AnNsJWF2WtHfDIvmx5b JjCjTgdwiFZ3TxCAyikAvc99U/UHEV25bty3jOBCbA0PYwv+rTRd3N2XZ3zol16ezMCx Tw== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 2vek4qaajj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 08 Oct 2019 02:18:46 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x982Icdi038981; Tue, 8 Oct 2019 02:18:45 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 2vg2055rtr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 08 Oct 2019 02:18:45 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x982Hcmr015945; Tue, 8 Oct 2019 02:17:38 GMT Received: from [10.191.3.27] (/10.191.3.27) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 07 Oct 2019 19:17:38 -0700 Subject: Re: [PATCH v4 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks To: Boris Ostrovsky , linux-kernel@vger.kernel.org Cc: vkuznets@redhat.com, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, sashal@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, pbonzini@redhat.com, rkrcmar@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, jgross@suse.com, sstabellini@kernel.org, peterz@infradead.org, Jonathan Corbet , "H. Peter Anvin" , Will Deacon References: <1570111335-12731-1-git-send-email-zhenzhong.duan@oracle.com> <1570111335-12731-2-git-send-email-zhenzhong.duan@oracle.com> <26ef7beb-dad0-13c9-fc2f-217a5e046e4d@oracle.com> From: Zhenzhong Duan Organization: Oracle Corporation Message-ID: Date: Tue, 8 Oct 2019 10:17:29 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9403 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 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-1910080023 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9403 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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-1910080023 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/10/7 22:46, Boris Ostrovsky wrote: > On 10/6/19 3:49 AM, Zhenzhong Duan wrote: >> On 2019/10/4 22:52, Boris Ostrovsky wrote: >> >>> On 10/3/19 10:02 AM, Zhenzhong Duan wrote: >>>>   void __init kvm_spinlock_init(void) >>>>   { >>>> -    /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ >>>> -    if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) >>>> -        return; >>>> - >>>> -    if (kvm_para_has_hint(KVM_HINTS_REALTIME)) >>>> +    /* >>>> +     * Don't use the pvqspinlock code if no KVM_FEATURE_PV_UNHALT >>>> feature >>>> +     * support, or there is REALTIME hints or only 1 vCPU. >>>> +     */ >>>> +    if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) || >>>> +        kvm_para_has_hint(KVM_HINTS_REALTIME) || >>>> +        num_possible_cpus() == 1) { >>>> +        pr_info("PV spinlocks disabled\n"); >>>>           return; >>>> +    } >>>>   -    /* Don't use the pvqspinlock code if there is only 1 vCPU. */ >>>> -    if (num_possible_cpus() == 1) >>>> +    if (nopvspin) { >>>> +        pr_info("PV spinlocks disabled forced by \"nopvspin\" >>>> parameter.\n"); >>>> +        static_branch_disable(&virt_spin_lock_key); >>> Would it make sense to bring here the other site where the key is >>> disabled (in kvm_smp_prepare_cpus())? >> Thanks for point out, I'll do it. Just not clear if I should do that >> in a separate patch, >> there is a history about that code: >> >> Its original place was here and then moved to kvm_smp_prepare_cpus() >> by below commit: >> 34226b6b ("KVM: X86: Fix setup the virt_spin_lock_key before static >> key get initialized") >> which fixed jump_label_init() calling late issue. >> >> Then 8990cac6 ("x86/jump_label: Initialize static branching early") >> move jump_label_init() >> early, so commit 34226b6b could be reverted. > Which is similar to what you did earlier for Xen. You remember that, ok, I'll do the same for KVM. Thanks Zhenzhong