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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 5F002C433E1 for ; Tue, 28 Jul 2020 10:09:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4283D20792 for ; Tue, 28 Jul 2020 10:09:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728690AbgG1KJX (ORCPT ); Tue, 28 Jul 2020 06:09:23 -0400 Received: from verein.lst.de ([213.95.11.211]:47569 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727973AbgG1KJW (ORCPT ); Tue, 28 Jul 2020 06:09:22 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 1FA8868B05; Tue, 28 Jul 2020 12:09:19 +0200 (CEST) Date: Tue, 28 Jul 2020 12:09:18 +0200 From: Christoph Hellwig To: Nicolas Saenz Julienne Cc: Christoph Hellwig , Amit Pundir , Marek Szyprowski , Robin Murphy , David Rientjes , linux-rpi-kernel@lists.infradead.org, jeremy.linton@arm.com, iommu@lists.linux-foundation.org, lkml , John Stultz , Sumit Semwal Subject: Re: [PATCH] dma-pool: Do not allocate pool memory from CMA Message-ID: <20200728100918.GA26364@lst.de> References: <01831596e4a2a6c9c066138b23bd30435f8e5569.camel@suse.de> <6db722947546221ed99d3f473f78e1a6de65d7d6.camel@suse.de> <0dc1e922bf87fa73790e7471b3974528dd261486.camel@suse.de> <20200724134114.GA3152@lst.de> <20200728091335.GA23744@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 28, 2020 at 11:30:32AM +0200, Nicolas Saenz Julienne wrote: > On Tue, 2020-07-28 at 11:13 +0200, Christoph Hellwig wrote: > > On Mon, Jul 27, 2020 at 07:56:56PM +0200, Nicolas Saenz Julienne wrote: > > > Hi Christoph, > > > thanks for having a look at this! > > > > > > On Fri, 2020-07-24 at 15:41 +0200, Christoph Hellwig wrote: > > > > Yes, the iommu is an interesting case, and the current code is > > > > wrong for that. > > > > > > Care to expand on this? I do get that checking dma_coherent_ok() on memory > > > that'll later on be mapped into an iommu is kind of silly, although I think > > > harmless in Amir's specific case, since devices have wide enough dma- > ranges. > > > Is > > > there more to it? > > > > I think the problem is that it can lead to not finding suitable memory. > > > > > > Can you try the patch below? It contains a modified version of Nicolas' > > > > patch to try CMA again for the expansion and a new (for now hackish) way > > > > to > > > > not apply the addressability check for dma-iommu allocations. > > > > > > > > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c > > > > index 6bc74a2d51273e..ec5e525d2b9309 100644 > > > > --- a/kernel/dma/pool.c > > > > +++ b/kernel/dma/pool.c > > > > @@ -3,7 +3,9 @@ > > > > * Copyright (C) 2012 ARM Ltd. > > > > * Copyright (C) 2020 Google LLC > > > > */ > > > > +#include > > > > #include > > > > +#include > > > > #include > > > > #include > > > > #include > > > > @@ -55,6 +57,31 @@ static void dma_atomic_pool_size_add(gfp_t gfp, size_t > > > > size) > > > > pool_size_kernel += size; > > > > } > > > > > > > > +static bool cma_in_zone(gfp_t gfp) > > > > +{ > > > > + phys_addr_t end; > > > > + unsigned long size; > > > > + struct cma *cma; > > > > + > > > > + cma = dev_get_cma_area(NULL); > > > > + if (!cma) > > > > + return false; > > > > + > > > > + size = cma_get_size(cma); > > > > + if (!size) > > > > + return false; > > > > + end = cma_get_base(cma) - memblock_start_of_DRAM() + size - 1; > > > > + > > > > + /* CMA can't cross zone boundaries, see cma_activate_area() */ > > > > + if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA) && > > > > + end <= DMA_BIT_MASK(zone_dma_bits)) > > > > + return true; > > > > + if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32) && > > > > + end <= DMA_BIT_MASK(32)) > > > > + return true; > > > > + return true; > > > > > > IIUC this will always return true given a CMA is present. Which reverts to > > > the > > > previous behaviour (previous as in breaking some rpi4 setups), isn't it? > > > > Was that really what broke the PI? I'll try to get the split out series > > today, which might have a few more tweaks, and then we'll need to test it > > both on these rpi4 setups and Amits phone. > > There was two issues with RPi: > - Not validating that pool allocated memory was OK for the device > - Locating all atomic pools in CMA, which doesn't work for all RPi4 devices*, > and IMO misses the point of having multiple pools. > > * With ACPI RPi4 we have CMA located in ZONE_DMA32, yet have an atomic pool > consumer, PCIe, that only wants memory in the [0 3GB] area, effectively needing > ZONE_DMA memory. Ok, I found a slight bug that wasn't intended. I wanted to make sure we can always fall back to a lower pool, but got that wrong. Should be fixed in the next version.