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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 CDB78C433E0 for ; Wed, 31 Mar 2021 11:50:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8EB816199A for ; Wed, 31 Mar 2021 11:50:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235309AbhCaLuF (ORCPT ); Wed, 31 Mar 2021 07:50:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:58328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235287AbhCaLty (ORCPT ); Wed, 31 Mar 2021 07:49:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EC88860249; Wed, 31 Mar 2021 11:49:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617191393; bh=9Tvk8pMagcUqHlxEfpmAq3P1z5xVSb6AxBC9iuF3UAo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kMlovUr/+JWR2ZHUYmDPMJ2ndHmdrz5lm7unGTt4nXLsAYiYuNHKr5e0oMkxx6fDz QR2rHHP5l9HS5rEud3McAg/yhn1jEjy25vdtAyZhr/OaEDrBLA51RShgMt6ADFGgKk uQaFZLkdzt19pPW2qgqzcDG9l8DRiLheZZlrvUgMDXhydKLRJqDVIU4Tnw+ks2cwPl dKj97SK7OA1MiDUHwOiBDXkDUo1pSJ37y/5yx0ulUHqGh/GEBy/gsrfNl6Wm5GhbkI DEukmD+vjCBTbLqtDliJ10g6+dV8RwrdEMhaaSt1c6K7yQWHZYOPwwIVQ8ExC6hyFf jZwkG9F4BmZKw== Date: Wed, 31 Mar 2021 12:49:47 +0100 From: Will Deacon To: Robin Murphy Cc: Christoph Hellwig , Joerg Roedel , Li Yang , Michael Ellerman , David Woodhouse , Lu Baolu , linuxppc-dev@lists.ozlabs.org, linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH 16/18] iommu: remove DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE Message-ID: <20210331114947.GA7626@willie-the-truck> References: <20210316153825.135976-1-hch@lst.de> <20210316153825.135976-17-hch@lst.de> <20210330131149.GP5908@willie-the-truck> <20210330135801.GA6187@willie-the-truck> <578d6aa5-4239-f5d7-2e9f-686b18e52bba@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <578d6aa5-4239-f5d7-2e9f-686b18e52bba@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Mar 30, 2021 at 05:28:19PM +0100, Robin Murphy wrote: > On 2021-03-30 14:58, Will Deacon wrote: > > On Tue, Mar 30, 2021 at 02:19:38PM +0100, Robin Murphy wrote: > > > On 2021-03-30 14:11, Will Deacon wrote: > > > > On Tue, Mar 16, 2021 at 04:38:22PM +0100, Christoph Hellwig wrote: > > > > > From: Robin Murphy > > > > > > > > > > Instead make the global iommu_dma_strict paramete in iommu.c canonical by > > > > > exporting helpers to get and set it and use those directly in the drivers. > > > > > > > > > > This make sure that the iommu.strict parameter also works for the AMD and > > > > > Intel IOMMU drivers on x86. As those default to lazy flushing a new > > > > > IOMMU_CMD_LINE_STRICT is used to turn the value into a tristate to > > > > > represent the default if not overriden by an explicit parameter. > > > > > > > > > > Signed-off-by: Robin Murphy . > > > > > [ported on top of the other iommu_attr changes and added a few small > > > > > missing bits] > > > > > Signed-off-by: Christoph Hellwig > > > > > --- > > > > > drivers/iommu/amd/iommu.c | 23 +------- > > > > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 50 +--------------- > > > > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 - > > > > > drivers/iommu/arm/arm-smmu/arm-smmu.c | 27 +-------- > > > > > drivers/iommu/dma-iommu.c | 9 +-- > > > > > drivers/iommu/intel/iommu.c | 64 ++++----------------- > > > > > drivers/iommu/iommu.c | 27 ++++++--- > > > > > include/linux/iommu.h | 4 +- > > > > > 8 files changed, 40 insertions(+), 165 deletions(-) > > > > > > > > I really like this cleanup, but I can't help wonder if it's going in the > > > > wrong direction. With SoCs often having multiple IOMMU instances and a > > > > distinction between "trusted" and "untrusted" devices, then having the > > > > flush-queue enabled on a per-IOMMU or per-domain basis doesn't sound > > > > unreasonable to me, but this change makes it a global property. > > > > > > The intent here was just to streamline the existing behaviour of stuffing a > > > global property into a domain attribute then pulling it out again in the > > > illusion that it was in any way per-domain. We're still checking > > > dev_is_untrusted() before making an actual decision, and it's not like we > > > can't add more factors at that point if we want to. > > > > Like I say, the cleanup is great. I'm just wondering whether there's a > > better way to express the complicated logic to decide whether or not to use > > the flush queue than what we end up with: > > > > if (!cookie->fq_domain && (!dev || !dev_is_untrusted(dev)) && > > domain->ops->flush_iotlb_all && !iommu_get_dma_strict()) > > > > which is mixing up globals, device properties and domain properties. The > > result is that the driver code ends up just using the global to determine > > whether or not to pass IO_PGTABLE_QUIRK_NON_STRICT to the page-table code, > > which is a departure from the current way of doing things. > > But previously, SMMU only ever saw the global policy piped through the > domain attribute by iommu_group_alloc_default_domain(), so there's no > functional change there. For DMA domains sure, but I don't think that's the case for unmanaged domains such as those used by VFIO. > Obviously some of the above checks could be factored out into some kind of > iommu_use_flush_queue() helper that IOMMU drivers can also call if they need > to keep in sync. Or maybe we just allow iommu-dma to set > IO_PGTABLE_QUIRK_NON_STRICT directly via iommu_set_pgtable_quirks() if we're > treating that as a generic thing now. I think a helper that takes a domain would be a good starting point. Will