From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DFB3E28E2 for ; Mon, 7 Nov 2022 10:54:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09D53C433D6; Mon, 7 Nov 2022 10:54:39 +0000 (UTC) Date: Mon, 7 Nov 2022 10:54:36 +0000 From: Catalin Marinas To: Christoph Hellwig Cc: Linus Torvalds , Arnd Bergmann , Greg Kroah-Hartman , Will Deacon , Marc Zyngier , Andrew Morton , Herbert Xu , Ard Biesheuvel , Isaac Manjarres , Saravana Kannan , Alasdair Kergon , Daniel Vetter , Joerg Roedel , Mark Brown , Mike Snitzer , "Rafael J. Wysocki" , Robin Murphy , linux-mm@kvack.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 03/13] iommu/dma: Force bouncing of the size is not cacheline-aligned Message-ID: References: <20221106220143.2129263-1-catalin.marinas@arm.com> <20221106220143.2129263-4-catalin.marinas@arm.com> <20221107094603.GB6055@lst.de> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221107094603.GB6055@lst.de> On Mon, Nov 07, 2022 at 10:46:03AM +0100, Christoph Hellwig wrote: > > +static inline bool dma_sg_kmalloc_needs_bounce(struct device *dev, > > + struct scatterlist *sg, int nents, > > + enum dma_data_direction dir) > > +{ > > + struct scatterlist *s; > > + int i; > > + > > + if (!IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) || > > + dir == DMA_TO_DEVICE || dev_is_dma_coherent(dev)) > > + return false; > > This part should be shared with dma-direct in a well documented helper. > > > + for_each_sg(sg, s, nents, i) { > > + if (dma_kmalloc_needs_bounce(dev, s->length, dir)) > > + return true; > > + } > > And for this loop iteration I'd much prefer it to be out of line, and > also not available in a global helper. > > But maybe someone can come up with a nice tweak to the dma-iommu > code to not require the extra sglist walk anyway. An idea: we could add another member to struct scatterlist to track the bounced address. We can then do the bouncing in a similar way to iommu_dma_map_sg_swiotlb() but without the iova allocation. The latter would be a common path for both the bounced and non-bounced cases. -- Catalin 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1B93FC4332F for ; Mon, 7 Nov 2022 10:55:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=zzFWLteVF2dpB8KUWcMRRCq1R4ftzkSZbqMfOB9H3IU=; b=bdj89CR05gEqSx FCXBnYDTZVA5/y6Nw2ohSnYxivukNLxQJDMhqZDLzgXZyvQ0YMj3HranVfLyspkaWaYZo5Niry1Xk pn+c3hxV5hCx0vs4Hkz8oUYcG0T7cCZWHUCfnipPJ31XxLxHnBU7ilGLFODMuGQ/NKLItjujnH9RE PyCvvxdpyPexIfqI5AeaArDNRUVFdIh+vxr6naMrxXpAvRvoBR93DS2y+FAIaLClbx1EDEKA8Qxky y7kkTxV0y8Ozv1cuKeeIODVCV0ujtuW6jeWsUcotmvzSxqo9Qmdfy2Co+oyh1eetGHKtqNQO+tF25 67ZjQFjfShGpaKVaqOfw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1orzmC-00DqGn-O1; Mon, 07 Nov 2022 10:54:48 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1orzm9-00DqDA-6F for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 10:54:46 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 26EAD60F99; Mon, 7 Nov 2022 10:54:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09D53C433D6; Mon, 7 Nov 2022 10:54:39 +0000 (UTC) Date: Mon, 7 Nov 2022 10:54:36 +0000 From: Catalin Marinas To: Christoph Hellwig Cc: Linus Torvalds , Arnd Bergmann , Greg Kroah-Hartman , Will Deacon , Marc Zyngier , Andrew Morton , Herbert Xu , Ard Biesheuvel , Isaac Manjarres , Saravana Kannan , Alasdair Kergon , Daniel Vetter , Joerg Roedel , Mark Brown , Mike Snitzer , "Rafael J. Wysocki" , Robin Murphy , linux-mm@kvack.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 03/13] iommu/dma: Force bouncing of the size is not cacheline-aligned Message-ID: References: <20221106220143.2129263-1-catalin.marinas@arm.com> <20221106220143.2129263-4-catalin.marinas@arm.com> <20221107094603.GB6055@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20221107094603.GB6055@lst.de> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_025445_289326_D6063525 X-CRM114-Status: GOOD ( 19.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Nov 07, 2022 at 10:46:03AM +0100, Christoph Hellwig wrote: > > +static inline bool dma_sg_kmalloc_needs_bounce(struct device *dev, > > + struct scatterlist *sg, int nents, > > + enum dma_data_direction dir) > > +{ > > + struct scatterlist *s; > > + int i; > > + > > + if (!IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) || > > + dir == DMA_TO_DEVICE || dev_is_dma_coherent(dev)) > > + return false; > > This part should be shared with dma-direct in a well documented helper. > > > + for_each_sg(sg, s, nents, i) { > > + if (dma_kmalloc_needs_bounce(dev, s->length, dir)) > > + return true; > > + } > > And for this loop iteration I'd much prefer it to be out of line, and > also not available in a global helper. > > But maybe someone can come up with a nice tweak to the dma-iommu > code to not require the extra sglist walk anyway. An idea: we could add another member to struct scatterlist to track the bounced address. We can then do the bouncing in a similar way to iommu_dma_map_sg_swiotlb() but without the iova allocation. The latter would be a common path for both the bounced and non-bounced cases. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel