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=-5.2 required=3.0 tests=BAYES_00, 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 E17A8C48BE5 for ; Tue, 22 Jun 2021 12:11:25 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 9A9CC60FF1 for ; Tue, 22 Jun 2021 12:11:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A9CC60FF1 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 smtp1.osuosl.org (Postfix) with ESMTP id 6ACB583938; Tue, 22 Jun 2021 12:11:25 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MUU_Xh0gssbM; Tue, 22 Jun 2021 12:11:24 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp1.osuosl.org (Postfix) with ESMTPS id 6732A837EC; Tue, 22 Jun 2021 12:11:24 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 48AD1C001A; Tue, 22 Jun 2021 12:11:24 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 14EE7C000E for ; Tue, 22 Jun 2021 12:11:22 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id E270F83938 for ; Tue, 22 Jun 2021 12:11:21 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id rXWSm3fn_KL5 for ; Tue, 22 Jun 2021 12:11:21 +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 smtp1.osuosl.org (Postfix) with ESMTP id E6987837EC for ; Tue, 22 Jun 2021 12:11:20 +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 D5853ED1; Tue, 22 Jun 2021 05:11:19 -0700 (PDT) Received: from [10.57.9.136] (unknown [10.57.9.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 73A493F694; Tue, 22 Jun 2021 05:11:18 -0700 (PDT) Subject: Re: [PATCHv2 1/3] iommu/io-pgtable: Add a quirk to use tlb_flush_all() for partial walk flush To: Sai Prakash Ranjan References: <904f283c-f8b1-ba84-d010-eacc87bb53c5@arm.com> From: Robin Murphy Message-ID: <2b093b93-7fab-be35-59d8-4463c199719a@arm.com> Date: Tue, 22 Jun 2021 13:11:12 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB Cc: linux-arm-msm@vger.kernel.org, Douglas Anderson , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Thierry Reding , Will Deacon , linux-arm-kernel@lists.infradead.org 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 2021-06-22 08:11, Sai Prakash Ranjan wrote: > Hi Robin, > > On 2021-06-21 21:15, Robin Murphy wrote: >> On 2021-06-18 03:51, Sai Prakash Ranjan wrote: >>> Add a quirk IO_PGTABLE_QUIRK_TLB_INV_ALL to invalidate entire context >>> with tlb_flush_all() callback in partial walk flush to improve unmap >>> performance on select few platforms where the cost of over-invalidation >>> is less than the unmap latency. >> >> I still think this doesn't belong anywhere near io-pgtable at all. >> It's a driver-internal decision how exactly it implements a non-leaf >> invalidation, and that may be more complex than a predetermined >> boolean decision. For example, I've just realised for SMMUv3 we can't >> invalidate multiple levels of table at once with a range command, >> since if we assume the whole thing is mapped at worst-case page >> granularity we may fail to invalidate any parts which are mapped as >> intermediate-level blocks. If invalidating a 1GB region (with 4KB >> granule) means having to fall back to 256K non-range commands, we may >> not want to invalidate by VA then, even though doing so for a 2MB >> region is still optimal. >> >> It's also quite feasible that drivers might want to do this for leaf >> invalidations too - if you don't like issuing 512 commands to >> invalidate 2MB, do you like issuing 511 commands to invalidate 2044KB? >> - and at that point the logic really has to be in the driver anyway. >> > > Ok I will move this to tlb_flush_walk() functions in the drivers. In the > previous > v1 thread, you suggested to make the choice in iommu_get_dma_strict() test, > I assume you meant the test in iommu_dma_init_domain() with a flag or > was it > the leaf driver(ex:arm-smmu.c) test of iommu_get_dma_strict() in > init_domain? Yes, I meant literally inside the same condition where we currently set "pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;" in arm_smmu_init_domain_context(). > I am still a bit confused on where this flag would be? Should this be a > part > of struct iommu_domain? Well, if you were to rewrite the config with an alternative set of flush_ops at that point it would be implicit. For a flag, probably either in arm_smmu_domain or arm_smmu_impl. Maybe a flag would be less useful than generalising straight to a "maximum number of by-VA invalidations it's worth sending individually" threshold value? It's clear to me what overall shape and separation of responsibility is most logical, but beyond that I don't have a particularly strong opinion on the exact implementation; I've just been chucking ideas around :) Cheers, Robin. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu