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 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 0C863C677FC for ; Thu, 11 Oct 2018 18:06:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1CA820658 for ; Thu, 11 Oct 2018 18:06:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1CA820658 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 S1728605AbeJLBey (ORCPT ); Thu, 11 Oct 2018 21:34:54 -0400 Received: from foss.arm.com ([217.140.101.70]:41948 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726699AbeJLBex (ORCPT ); Thu, 11 Oct 2018 21:34:53 -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 2A9E5ED1; Thu, 11 Oct 2018 11:06:34 -0700 (PDT) Received: from [10.1.196.75] (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E99033F5D3; Thu, 11 Oct 2018 11:06:32 -0700 (PDT) Subject: Re: [PATCH 03/10] swiotlb: do not panic on mapping failures To: Christoph Hellwig , Will Deacon , Catalin Marinas , Konrad Rzeszutek Wilk Cc: linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20181008080246.20543-1-hch@lst.de> <20181008080246.20543-4-hch@lst.de> From: Robin Murphy Message-ID: Date: Thu, 11 Oct 2018 19:06:31 +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: <20181008080246.20543-4-hch@lst.de> 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 On 08/10/18 09:02, Christoph Hellwig wrote: > All properly written drivers now have error handling in the > dma_map_single / dma_map_page callers. As swiotlb_tbl_map_single already > prints a useful warning when running out of swiotlb pool swace we can > also remove swiotlb_full entirely as it serves no purpose now. $ git grep -l 'dma_map_\(page\|single\)' drivers/ | wc -l 385 $ git grep -l dma_mapping_error drivers/ | wc -l 396 Close enough, to first approximation :D I agree the other (non-fatal) warning seems sufficient, and frankly the panic can be a bit of a pain for development sometimes. Reviewed-by: Robin Murphy > Signed-off-by: Christoph Hellwig > --- > kernel/dma/swiotlb.c | 33 +-------------------------------- > 1 file changed, 1 insertion(+), 32 deletions(-) > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 26d3af52956f..69bf305ee5f8 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -761,34 +761,6 @@ static bool swiotlb_free_buffer(struct device *dev, size_t size, > return true; > } > > -static void > -swiotlb_full(struct device *dev, size_t size, enum dma_data_direction dir, > - int do_panic) > -{ > - if (swiotlb_force == SWIOTLB_NO_FORCE) > - return; > - > - /* > - * Ran out of IOMMU space for this operation. This is very bad. > - * Unfortunately the drivers cannot handle this operation properly. > - * unless they check for dma_mapping_error (most don't) > - * When the mapping is small enough return a static buffer to limit > - * the damage, or panic when the transfer is too big. > - */ > - dev_err_ratelimited(dev, "DMA: Out of SW-IOMMU space for %zu bytes\n", > - size); > - > - if (size <= io_tlb_overflow || !do_panic) > - return; > - > - if (dir == DMA_BIDIRECTIONAL) > - panic("DMA: Random memory could be DMA accessed\n"); > - if (dir == DMA_FROM_DEVICE) > - panic("DMA: Random memory could be DMA written\n"); > - if (dir == DMA_TO_DEVICE) > - panic("DMA: Random memory could be DMA read\n"); > -} > - > /* > * Map a single buffer of the indicated size for DMA in streaming mode. The > * physical address to use is returned. > @@ -817,10 +789,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page, > > /* Oh well, have to allocate and map a bounce buffer. */ > map = map_single(dev, phys, size, dir, attrs); > - if (map == SWIOTLB_MAP_ERROR) { > - swiotlb_full(dev, size, dir, 1); > + if (map == SWIOTLB_MAP_ERROR) > return __phys_to_dma(dev, io_tlb_overflow_buffer); > - } > > dev_addr = __phys_to_dma(dev, map); > > @@ -948,7 +918,6 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems, > if (map == SWIOTLB_MAP_ERROR) { > /* Don't panic here, we expect map_sg users > to do proper error handling. */ > - swiotlb_full(hwdev, sg->length, dir, 0); > attrs |= DMA_ATTR_SKIP_CPU_SYNC; > swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir, > attrs); >