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,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 6C9A5C433E7 for ; Fri, 9 Oct 2020 17:11:02 +0000 (UTC) Received: from whitealder.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 0DF2022267 for ; Fri, 9 Oct 2020 17:11:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0DF2022267 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 whitealder.osuosl.org (Postfix) with ESMTP id A053187801; Fri, 9 Oct 2020 17:11:01 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id iXsGiLKGySZA; Fri, 9 Oct 2020 17:11:00 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id BDA8587720; Fri, 9 Oct 2020 17:11:00 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8F4E1C07FF; Fri, 9 Oct 2020 17:11:00 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5EF3DC0051 for ; Fri, 9 Oct 2020 17:10:58 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 46F1687148 for ; Fri, 9 Oct 2020 17:10:58 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id zyqds9aIZ4Bm for ; Fri, 9 Oct 2020 17:10:57 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 173A987126 for ; Fri, 9 Oct 2020 17:10:57 +0000 (UTC) Received: from gaia (unknown [95.149.105.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8A42E22267; Fri, 9 Oct 2020 17:10:54 +0000 (UTC) Date: Fri, 9 Oct 2020 18:10:52 +0100 From: Catalin Marinas To: Ard Biesheuvel Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711 Message-ID: <20201009171051.GL23638@gaia> References: <20201001172320.GQ21544@gaia> <20201002115541.GC7034@gaia> <12f33d487eabd626db4c07ded5a1447795eed355.camel@suse.de> <20201009071013.GA12208@lst.de> <513833810c15b5efeab7c3cbae1963a78c71a79f.camel@suse.de> <20201009152433.GA19953@e121166-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Linux ARM , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Frank Rowand , Linux Kernel Mailing List , Linux Memory Management List , iommu@lists.linux-foundation.org, Rob Herring , linux-rpi-kernel@lists.infradead.org, Will Deacon , Christoph Hellwig , Robin Murphy 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Fri, Oct 09, 2020 at 06:23:06PM +0200, Ard Biesheuvel wrote: > On Fri, 9 Oct 2020 at 17:24, Lorenzo Pieralisi > wrote: > > We can move this check to IORT code and call it from arm64 if it > > can be made to work. > > Finding the smallest value in the IORT, and assigning it to > zone_dma_bits if it is < 32 should be easy. But as I understand it, > having these separate DMA and DMA32 zones is what breaks kdump, no? So > how is this going to fix the underlying issue? If zone_dma_bits is 32, ZONE_DMA32 disappears into ZONE_DMA (GFP_DMA32 allocations fall back to ZONE_DMA). kdump wants DMA-able memory and, without a 30-bit ZONE_DMA, that would be the bottom 32-bit. With the introduction of ZONE_DMA, this suddenly became 1GB. We could change kdump to allocate ZONE_DMA32 but this one may also be small as it lost 1GB to ZONE_DMA. However, the kdump kernel would need to be rebuilt without ZONE_DMA since it won't have any. IIRC (it's been a while since I looked), the kdump allocation couldn't span multiple zones. In a separate thread, we try to fix kdump to use allocations above 4G as a fallback but this only fixes platforms with enough RAM (and maybe it's only those platforms that care about kdump). -- Catalin _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu