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 82375C433C1 for ; Wed, 31 Mar 2021 09:58:51 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 1768E61878 for ; Wed, 31 Mar 2021 09:58:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1768E61878 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id C552E60AA9; Wed, 31 Mar 2021 09:58:50 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qWo0JHkAW7Gd; Wed, 31 Mar 2021 09:58:49 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTP id 98EB8607B0; Wed, 31 Mar 2021 09:58:49 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6823FC000B; Wed, 31 Mar 2021 09:58:49 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 78087C000A for ; Wed, 31 Mar 2021 09:58:47 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 72F844063D for ; Wed, 31 Mar 2021 09:58:47 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 2vdwWLk5I5oZ for ; Wed, 31 Mar 2021 09:58:43 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp4.osuosl.org (Postfix) with ESMTP id B86C8405F0 for ; Wed, 31 Mar 2021 09:58:43 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9CB561042; Wed, 31 Mar 2021 02:58:42 -0700 (PDT) Received: from [10.57.24.208] (unknown [10.57.24.208]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E5A3F3F792; Wed, 31 Mar 2021 02:58:40 -0700 (PDT) Subject: Re: [PATCH 1/6] iommu: Move IOVA power-of-2 roundup into allocator To: John Garry , "joro@8bytes.org" , "will@kernel.org" , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "hch@lst.de" , "m.szyprowski@samsung.com" 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> <08c0f4b9-8713-fa97-3986-3cfb0d6b820b@huawei.com> From: Robin Murphy Message-ID: Date: Wed, 31 Mar 2021 10:58:36 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <08c0f4b9-8713-fa97-3986-3cfb0d6b820b@huawei.com> Content-Language: en-GB Cc: "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-scsi@vger.kernel.org" , Linuxarm X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2021-03-22 15:01, John Garry wrote: > 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. Sorry if the phrasing was unclear there - the allusion to default domains is new, it just occurred to me that what we do there is in fact fairly close to what I've suggested previously for this. In that case, we have a global policy set by the command line, which *can* be overridden per-domain via sysfs at runtime, provided the user is willing to tear the whole thing down. Using a similar approach here would give a fair degree of flexibility but still mean that changes never have to be made dynamically to a live domain. Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu