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=-5.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 B6CD3C47096 for ; Thu, 3 Jun 2021 08:00:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 948DC613AE for ; Thu, 3 Jun 2021 08:00:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229661AbhFCICk (ORCPT ); Thu, 3 Jun 2021 04:02:40 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3134 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229486AbhFCICi (ORCPT ); Thu, 3 Jun 2021 04:02:38 -0400 Received: from fraeml736-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FwdLK2htKz6J9Tk; Thu, 3 Jun 2021 15:48:25 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml736-chm.china.huawei.com (10.206.15.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 3 Jun 2021 10:00:52 +0200 Received: from [10.47.80.115] (10.47.80.115) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 3 Jun 2021 09:00:51 +0100 Subject: Re: [PATCH v3 0/7] iommu: Allow IOVA rcache range be configured To: Lu Baolu , , , CC: , , References: <1622557781-211697-1-git-send-email-john.garry@huawei.com> <834ad35a-7310-1738-7d17-7c061ca73e4c@linux.intel.com> <1cbf8cc2-8cee-0579-2514-56f664baa9cd@huawei.com> <5e6ff4d6-cd67-d4ab-814c-e10a258191b1@linux.intel.com> From: John Garry Message-ID: <74dd66d6-315c-3273-afaa-e6164b4ea33f@huawei.com> Date: Thu, 3 Jun 2021 09:00:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <5e6ff4d6-cd67-d4ab-814c-e10a258191b1@linux.intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.80.115] X-ClientProxiedBy: lhreml751-chm.china.huawei.com (10.201.108.201) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/06/2021 01:39, Lu Baolu wrote: >> I did actually try increasing the range for a 'live' domain in the v1 >> series, but it turned out too messy. First problem is reallocating the >> memory to hold the rcaches. Second problem is that we need to deal >> with the issue that all IOVAs in the rcache need to be a pow-of-2, >> which is difficult to enforce for IOVAs which weren't being cached >> before, but now would be. >> >> So now I changed to work similar to how we change the default domain >> type, i.e. don't operate on a 'live' domain. > > If these hard restrictions on users are just to walk around the messy > code in kernel, I would rather solve those messy code to achieve a > better user experience. :-) Hi Baolu, It's not that the code is messy. I'm just saying that it's difficult to change the rcache range of a live domain. So we take an approach similar to changing the domain default type - it is more straightforward to configure the rcache range that way. Anyway, it would be great if you or anyone could look at the code so that some progress can be made here. Thanks, John