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=-5.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 DEF5BC43461 for ; Wed, 16 Sep 2020 08:39:36 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 84C682064E for ; Wed, 16 Sep 2020 08:39:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=xen.org header.i=@xen.org header.b="XZYT278W" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84C682064E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kISy7-0001Ht-7K; Wed, 16 Sep 2020 08:39:11 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kISy5-0001Hn-TY for xen-devel@lists.xenproject.org; Wed, 16 Sep 2020 08:39:09 +0000 X-Inumbo-ID: 714ce9e2-8ae8-42ec-aa19-f4b4e419681e Received: from mail.xenproject.org (unknown [104.130.215.37]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 714ce9e2-8ae8-42ec-aa19-f4b4e419681e; Wed, 16 Sep 2020 08:39:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=BnkhvH6sWDyVA1Sfr+BaWdUapx4x+u5a00QxBAhNGvY=; b=XZYT278WtF5hH/2WAcNQNuYSR1 bowf2Qqh8/YxWE04gU59+e8AoEnaB3eU9fbzBjjGv7FePnJ2hmKZTzkHxXFXIolQchtCLmIWjHimV o6klK+D8VArZIx9xnKONNonRlOkY6qzTrhyM/gOyIk1XPKsH7ovfFsAaTkmgaVcNiUUw=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kISy1-0000nx-K8; Wed, 16 Sep 2020 08:39:05 +0000 Received: from [54.239.6.187] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1kISy1-00012b-9R; Wed, 16 Sep 2020 08:39:05 +0000 Subject: Re: [PATCH V1 11/16] xen/ioreq: Introduce hvm_domain_has_ioreq_server() To: paul@xen.org, 'Jan Beulich' , 'Oleksandr Tyshchenko' Cc: xen-devel@lists.xenproject.org, 'Oleksandr Tyshchenko' , 'Stefano Stabellini' , 'Volodymyr Babchuk' , 'Andrew Cooper' , 'Wei Liu' , =?UTF-8?B?J1JvZ2VyIFBhdSBNb25uw6kn?= , 'Julien Grall' References: <1599769330-17656-1-git-send-email-olekstysh@gmail.com> <1599769330-17656-12-git-send-email-olekstysh@gmail.com> <93cc6603-44f2-1ceb-997d-cbc51c3ba2c3@suse.com> <002801d68c01$44756ad0$cd604070$@xen.org> From: Julien Grall Message-ID: <63e51f84-c3ee-a894-5ea2-40cd3b6e26dc@xen.org> Date: Wed, 16 Sep 2020 09:39:02 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <002801d68c01$44756ad0$cd604070$@xen.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 16/09/2020 09:13, Paul Durrant wrote: >> -----Original Message----- >> From: Jan Beulich >> Sent: 16 September 2020 09:05 >> To: Oleksandr Tyshchenko ; Paul Durrant >> Cc: xen-devel@lists.xenproject.org; Oleksandr Tyshchenko ; Stefano >> Stabellini ; Julien Grall ; Volodymyr Babchuk >> ; Andrew Cooper ; Wei Liu ; Roger >> Pau Monné ; Julien Grall >> Subject: Re: [PATCH V1 11/16] xen/ioreq: Introduce hvm_domain_has_ioreq_server() >> >> On 10.09.2020 22:22, Oleksandr Tyshchenko wrote: >>> From: Oleksandr Tyshchenko >>> >>> This patch introduces a helper the main purpose of which is to check >>> if a domain is using IOREQ server(s). >>> >>> On Arm the benefit is to avoid calling handle_hvm_io_completion() >>> (which implies iterating over all possible IOREQ servers anyway) >>> on every return in leave_hypervisor_to_guest() if there is no active >>> servers for the particular domain. >>> > > Is this really worth it? The limit on the number of ioreq serves is small... just 8. When I suggested this, I failed to realize there was only 8 IOREQ servers available. However, I would not be surprised if this increase long term as we want to use > I doubt you'd be able measure the difference. Bear in mind that entry/exit to the hypervisor is pretty "cheap" on Arm compare to x86. So we want to avoid doing extra work if it is not necessary. Cheers, -- Julien Grall