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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B16F2C433DF for ; Fri, 3 Jul 2020 12:51:38 +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 878E220B80 for ; Fri, 3 Jul 2020 12:51:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 878E220B80 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com 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 1jrL9i-0008SD-0l; Fri, 03 Jul 2020 12:51:02 +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 1jrL9h-0008S8-11 for xen-devel@lists.xenproject.org; Fri, 03 Jul 2020 12:51:01 +0000 X-Inumbo-ID: d4e7e0d8-bd2b-11ea-89a0-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id d4e7e0d8-bd2b-11ea-89a0-12813bfff9fa; Fri, 03 Jul 2020 12:50:54 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E7D37ACA0; Fri, 3 Jul 2020 12:50:53 +0000 (UTC) Subject: Re: [PATCH v4 06/10] memory: batch processing in acquire_resource() To: Julien Grall References: <5be6cb58-82d0-0a78-a9b2-5c078b5d3587@xen.org> <004901d65128$16a6f330$43f4d990$@xen.org> <481e8ee7-561a-10d6-4358-7b07a8911ce8@xen.org> From: Jan Beulich Message-ID: <4fbc0a79-052e-0596-ca31-ec4902dddc85@suse.com> Date: Fri, 3 Jul 2020 14:50:56 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: , Cc: 'Stefano Stabellini' , tamas.lengyel@intel.com, 'Wei Liu' , paul@xen.org, 'Andrew Cooper' , =?UTF-8?B?J01pY2hhxYIgTGVzemN6ecWEc2tpJw==?= , 'Ian Jackson' , 'George Dunlap' , luwei.kang@intel.com, xen-devel@lists.xenproject.org Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 03.07.2020 13:36, Julien Grall wrote: > On 03/07/2020 12:22, Jan Beulich wrote: >> On 03.07.2020 13:17, Julien Grall wrote: >>> In the current implementation, we tell the guest how many frames it can >>> request in a batch. This number may be much smaller that the maximum >>> number of frames of the type. >>> >>> Furthermore this value is not tie to the xmar.type. Therefore, it is >>> valid for a guest to call this hypercall only once at boot to figure out >>> the maximum batch. >>> >>> So while the change you suggest looks a good idea, I don't think it is >>> possible to do that with the current hypercall. >> >> Doesn't the limit simply change to UINT_MAX >> MEMOP_EXTENT_SHIFT, >> which then is what should be reported? > > Hmmm... Can you remind me whether we support migration to an older release? I'm pretty sure we say "N -> N+1 only" somewhere, but this "somewhere" clearly isn't SUPPORT.md. Jan