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=-5.3 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 CF6FFC433E2 for ; Mon, 22 Mar 2021 15:04:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9ED42619B2 for ; Mon, 22 Mar 2021 15:04:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231469AbhCVPDn (ORCPT ); Mon, 22 Mar 2021 11:03:43 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2726 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229673AbhCVPDW (ORCPT ); Mon, 22 Mar 2021 11:03:22 -0400 Received: from fraeml701-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4F3yFk4McTz682dy; Mon, 22 Mar 2021 22:54:34 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml701-chm.china.huawei.com (10.206.15.50) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Mon, 22 Mar 2021 16:03:15 +0100 Received: from [10.210.167.192] (10.210.167.192) 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 15.1.2106.2; Mon, 22 Mar 2021 15:03:14 +0000 Subject: Re: [PATCH 1/6] iommu: Move IOVA power-of-2 roundup into allocator To: Robin Murphy , "joro@8bytes.org" , "will@kernel.org" , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "hch@lst.de" , "m.szyprowski@samsung.com" CC: "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-scsi@vger.kernel.org" , Linuxarm References: <1616160348-29451-1-git-send-email-john.garry@huawei.com> <1616160348-29451-2-git-send-email-john.garry@huawei.com> <73d459de-b5cc-e2f5-bcd7-2ee23c8d5075@huawei.com> From: John Garry Message-ID: <08c0f4b9-8713-fa97-3986-3cfb0d6b820b@huawei.com> Date: Mon, 22 Mar 2021 15:01:00 +0000 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: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.210.167.192] X-ClientProxiedBy: lhreml718-chm.china.huawei.com (10.201.108.69) 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 19/03/2021 19:20, Robin Murphy wrote: Hi Robin, >> So then we have the issue of how to dynamically increase this rcache >> threshold. The problem is that we may have many devices associated with >> the same domain. So, in theory, we can't assume that when we increase >> the threshold that some other device will try to fast free an IOVA which >> was allocated prior to the increase and was not rounded up. >> >> I'm very open to better (or less bad) suggestions on how to do this ... > ...but yes, regardless of exactly where it happens, rounding up or not > is the problem for rcaches in general. I've said several times that my > preferred approach is to not change it that dynamically at all, but > instead treat it more like we treat the default domain type. > Can you remind me of that idea? I don't remember you mentioning using default domain handling as a reference in any context. Thanks, John