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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 2FF44C67863 for ; Mon, 22 Oct 2018 17:31:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDCB620645 for ; Mon, 22 Oct 2018 17:31:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="R0hp0BDM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DDCB620645 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1728846AbeJWBvS (ORCPT ); Mon, 22 Oct 2018 21:51:18 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51760 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728628AbeJWBvS (ORCPT ); Mon, 22 Oct 2018 21:51:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=URkB75rJsVa2bCEpG8luURFvng73Q4+LU2k9AWbtWNY=; b=R0hp0BDMm/Llo0bD77eq5RWjB P8HbnUinZj7wgAeCUU0rbhTQaEeEZsaPsH3aswqrX4LuIHF0bH6VNDPTe47AcqX+NSaBsouqfuJ+t pB5m+fE2Yq//JuCV2c67eeKc2q6CHIp05kfqwZzSBZP1ND9L0SnW0CwhGHSMDbIdqOSm0ZPnzRFj+ c5idhfyganuuW6fzw3chE4efkUMe4lw6EF7s5SdAh18fFH8EqtuIocEj3nq+ZnafQn+QQobO161We KwhNIOGpAzzq1wt9Dez1LflaMg1X7cHyGaqvU3SfqKkNg6mAG2fd/9A43aLO3HqOl9xKmpXXb3COB ElMInPmqA==; Received: from [167.98.65.38] (helo=worktop) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gEe3O-0001xC-My; Mon, 22 Oct 2018 17:31:46 +0000 Received: by worktop (Postfix, from userid 1000) id 78DFC6E08C3; Mon, 22 Oct 2018 19:31:44 +0200 (CEST) Date: Mon, 22 Oct 2018 19:31:44 +0200 From: Peter Zijlstra To: Waiman Long Cc: Juergen Gross , Yi Sun , linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, chao.p.peng@intel.com, chao.gao@intel.com, isaku.yamahata@intel.com, michael.h.kelley@microsoft.com, tianyu.lan@microsoft.com, "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , "mingo@redhat.com" , Will Deacon Subject: Re: [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall Message-ID: <20181022173144.GB3109@worktop.c.hoisthospitality.com> References: <1539954835-34035-1-git-send-email-yi.y.sun@linux.intel.com> <1539954835-34035-3-git-send-email-yi.y.sun@linux.intel.com> <20181022015342.GK11769@yi.y.sun> <2e0d62cb-b706-a5b4-65f7-982a913fb32b@suse.com> <20181022171516.GH3117@worktop.programming.kicks-ass.net> <6d8095c0-af95-5967-3ca5-2ceeb74233ea@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6d8095c0-af95-5967-3ca5-2ceeb74233ea@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 22, 2018 at 01:27:27PM -0400, Waiman Long wrote: > >> I agree with Juergen on that. I would suggest rename the > >> vcpu_is_preempted hook into a more generic vcpu_stop_spinning, perhaps, > >> so different hypervisors can act on the information accordingly. Adding > >> an extra parameter is fine. > > No; no extra parameters. vcpu_is_preempted() is a simple and intuitive > > interface. Why would we want to make it complicated? > > Hyperv seems to do it in a somewhat different way by looking at the spin > counter and decide if it should continue. I don't know why they do that > and what advantage it has. > > The current patch is definitely not OK. A revised patch that makes use > of an existing paravirt hook will be more acceptable. Again, I would > like to see some performance figure and why they do it this way to see > if it is worthwhile to change the existing interface. Note that there are vcpu_is_preempted() users that are not in a spin-loop.