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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 83E9DECDFBB for ; Wed, 18 Jul 2018 13:28:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 48D972075A for ; Wed, 18 Jul 2018 13:28:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 48D972075A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731456AbeGROGA (ORCPT ); Wed, 18 Jul 2018 10:06:00 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50786 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726990AbeGROGA (ORCPT ); Wed, 18 Jul 2018 10:06:00 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BA3747C6CA; Wed, 18 Jul 2018 13:28:04 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-175.bos.redhat.com [10.18.17.175]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7729F178BA; Wed, 18 Jul 2018 13:28:04 +0000 (UTC) Subject: Re: [PATCH] x86/pvqspinlock: Use LOCK_PREFIX in __pv_queued_spin_unlock assembly code To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, x86@kernel.org, Will Deacon , Joe Mario References: <1531858560-21547-1-git-send-email-longman@redhat.com> <20180718081918.GO2494@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: <5d381d80-21c7-c8a7-db01-24fbbf8b1041@redhat.com> Date: Wed, 18 Jul 2018 09:28:04 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180718081918.GO2494@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 18 Jul 2018 13:28:04 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 18 Jul 2018 13:28:04 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/18/2018 04:19 AM, Peter Zijlstra wrote: > On Tue, Jul 17, 2018 at 04:16:00PM -0400, Waiman Long wrote: >> The LOCK_PREFIX macro should be used in the assembly >> __raw_callee_save___pv_queued_spin_unlock code so that the lock prefix >> can be patched out on UP systems. > True; but does paravirt locking realy make sense on UP guests? > Yes, it doesn't make sense. That is why I have another kvm patch that turns off pvqspinlock for UP guest. However, I am not that familiar with the Xen code. So I don't have a corresponding one for Xen. Cheers, Longman