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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 F01BFC433F4 for ; Fri, 21 Sep 2018 11:09:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A67AA20858 for ; Fri, 21 Sep 2018 11:09:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A67AA20858 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389845AbeIUQ6Q (ORCPT ); Fri, 21 Sep 2018 12:58:16 -0400 Received: from foss.arm.com ([217.140.101.70]:33870 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727554AbeIUQ6P (ORCPT ); Fri, 21 Sep 2018 12:58:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 344FD80D; Fri, 21 Sep 2018 04:09:53 -0700 (PDT) Received: from [10.4.12.131] (e110467-lin.emea.arm.com [10.4.12.131]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 431713F557; Fri, 21 Sep 2018 04:09:52 -0700 (PDT) Subject: Re: [PATCH] dma-debug: Check for drivers mapping vmalloc addresses To: Stephen Boyd , Christoph Hellwig Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Marek Szyprowski References: <20180920223559.136915-1-swboyd@chromium.org> From: Robin Murphy Message-ID: Date: Fri, 21 Sep 2018 12:09:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180920223559.136915-1-swboyd@chromium.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Stephen, On 20/09/18 23:35, Stephen Boyd wrote: > I recently debugged a DMA mapping oops where a driver was trying to map > a buffer returned from request_firmware() with dma_map_single(). Memory > returned from request_firmware() is mapped into the vmalloc region and > this isn't a valid region to map with dma_map_single() per the DMA > documentation's "What memory is DMA'able?" section. > > Unfortunately, we don't really check that in the DMA debugging code, so > enabling DMA debugging doesn't help catch this problem. Let's add a new > DMA debug function to check for a vmalloc address and print a warning if > this happens. This makes it a little easier to debug these sorts of > problems, instead of seeing odd behavior or crashes when drivers attempt > to map the vmalloc space for DMA. Good idea! > Cc: Marek Szyprowski > Cc: Robin Murphy > Signed-off-by: Stephen Boyd > --- > include/linux/dma-debug.h | 8 ++++++++ > include/linux/dma-mapping.h | 1 + > kernel/dma/debug.c | 12 ++++++++++++ > 3 files changed, 21 insertions(+) However I can't help thinking this looks a little heavyweight for a single specific check. It seems like it would be enough to simply pass the VA as an extra argument to debug_dma_map_page(), since we already have the map_single argument which would indicate when it's valid. What do you reckon? Robin. > diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h > index a785f2507159..5aec2ca8a426 100644 > --- a/include/linux/dma-debug.h > +++ b/include/linux/dma-debug.h > @@ -32,6 +32,9 @@ extern void dma_debug_add_bus(struct bus_type *bus); > > extern int dma_debug_resize_entries(u32 num_entries); > > +extern void debug_dma_check_vmalloc(struct device *dev, const void *addr, > + unsigned long len); > + > extern void debug_dma_map_page(struct device *dev, struct page *page, > size_t offset, size_t size, > int direction, dma_addr_t dma_addr, > @@ -103,6 +106,11 @@ static inline int dma_debug_resize_entries(u32 num_entries) > return 0; > } > > +static inline void debug_dma_check_vmalloc(struct device *dev, const void *addr, > + unsigned long len) > +{ > +} > + > static inline void debug_dma_map_page(struct device *dev, struct page *page, > size_t offset, size_t size, > int direction, dma_addr_t dma_addr, > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index eafd6f318e78..a0e67fd5433c 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -232,6 +232,7 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr, > dma_addr_t addr; > > BUG_ON(!valid_dma_direction(dir)); > + debug_dma_check_vmalloc(dev, ptr, size); > addr = ops->map_page(dev, virt_to_page(ptr), > offset_in_page(ptr), size, > dir, attrs); > diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c > index c007d25bee09..7ee7978868d4 100644 > --- a/kernel/dma/debug.c > +++ b/kernel/dma/debug.c > @@ -1312,6 +1312,18 @@ static void check_sg_segment(struct device *dev, struct scatterlist *sg) > #endif > } > > +void debug_dma_check_vmalloc(struct device *dev, const void *addr, > + unsigned long len) > +{ > + if (unlikely(dma_debug_disabled())) > + return; > + > + if (is_vmalloc_addr(addr)) > + err_printk(dev, NULL, "DMA-API: device driver maps memory from vmalloc area [addr=%p] [len=%lu]\n", > + addr, len); > +} > +EXPORT_SYMBOL(debug_dma_check_vmalloc); > + > void debug_dma_map_page(struct device *dev, struct page *page, size_t offset, > size_t size, int direction, dma_addr_t dma_addr, > bool map_single) >