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Mon, 04 Mar 2019 22:00:15 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x24M0EEw004579 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 4 Mar 2019 22:00:14 GMT Received: from abhmp0022.oracle.com (abhmp0022.oracle.com [141.146.116.28]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x24M0BGI022127; Mon, 4 Mar 2019 22:00:12 GMT Received: from char.us.oracle.com (/10.152.32.25) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 04 Mar 2019 14:00:11 -0800 Received: by char.us.oracle.com (Postfix, from userid 1000) id 3F2016A012E; Mon, 4 Mar 2019 17:00:10 -0500 (EST) Date: Mon, 4 Mar 2019 17:00:10 -0500 From: Konrad Rzeszutek Wilk To: Arnd Bergmann Cc: Boris Ostrovsky , Juergen Gross , Christoph Hellwig , Marek Szyprowski , Stefano Stabellini , Robin Murphy , Mike Rapoport , Andrew Morton , Joerg Roedel , xen-devel@lists.xenproject.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Revert "swiotlb: remove SWIOTLB_MAP_ERROR" Message-ID: <20190304220010.GD30350@char.us.oracle.com> References: <20190304195951.1118807-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190304195951.1118807-1-arnd@arndb.de> User-Agent: Mutt/1.9.1 (2017-09-22) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9185 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903040154 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 04, 2019 at 08:59:03PM +0100, Arnd Bergmann wrote: > This reverts commit b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR"), which > introduced an overflow warning in configurations that have a larger > dma_addr_t than phys_addr_t: > > In file included from include/linux/dma-direct.h:5, > from kernel/dma/swiotlb.c:23: > kernel/dma/swiotlb.c: In function 'swiotlb_tbl_map_single': > include/linux/dma-mapping.h:136:28: error: conversion from 'long long unsigned int' to 'phys_addr_t' {aka 'unsigned int'} changes value from '18446744073709551615' to '4294967295' [-Werror=overflow] > #define DMA_MAPPING_ERROR (~(dma_addr_t)0) > ^ > kernel/dma/swiotlb.c:544:9: note: in expansion of macro 'DMA_MAPPING_ERROR' > return DMA_MAPPING_ERROR; > > The configuration that caused this is on 32-bit ARM, where the DMA address > space depends on the enabled hardware platforms, while the physical > address space depends on the type of MMU chosen (classic vs LPAE). > > I tried a couple of alternative approaches, but the previous version > seems as good as any other, so I went back to that. That is really a bummer. What about making the phys_addr_t and dma_addr_t have the same width with some magic #ifdef hackery? > > Fixes: b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR") > Signed-off-by: Arnd Bergmann > --- > drivers/xen/swiotlb-xen.c | 4 ++-- > include/linux/swiotlb.h | 3 +++ > kernel/dma/swiotlb.c | 4 ++-- > 3 files changed, 7 insertions(+), 4 deletions(-) > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index 877baf2a94f4..57a98279bf4f 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -406,7 +406,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, > > map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir, > attrs); > - if (map == DMA_MAPPING_ERROR) > + if (map == SWIOTLB_MAP_ERROR) > return DMA_MAPPING_ERROR; > > dev_addr = xen_phys_to_bus(map); > @@ -557,7 +557,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, > sg_phys(sg), > sg->length, > dir, attrs); > - if (map == DMA_MAPPING_ERROR) { > + if (map == SWIOTLB_MAP_ERROR) { > dev_warn(hwdev, "swiotlb buffer is full\n"); > /* Don't panic here, we expect map_sg users > to do proper error handling. */ > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h > index 361f62bb4a8e..a65a36551f58 100644 > --- a/include/linux/swiotlb.h > +++ b/include/linux/swiotlb.h > @@ -44,6 +44,9 @@ enum dma_sync_target { > SYNC_FOR_DEVICE = 1, > }; > > +/* define the last possible byte of physical address space as a mapping error */ > +#define SWIOTLB_MAP_ERROR (~(phys_addr_t)0x0) > + > extern phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, > dma_addr_t tbl_dma_addr, > phys_addr_t phys, size_t size, > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 12059b78b631..922880b84387 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -541,7 +541,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, > spin_unlock_irqrestore(&io_tlb_lock, flags); > if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit()) > dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size); > - return DMA_MAPPING_ERROR; > + return SWIOTLB_MAP_ERROR; > found: > io_tlb_used += nslots; > spin_unlock_irqrestore(&io_tlb_lock, flags); > @@ -659,7 +659,7 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr, > /* Oh well, have to allocate and map a bounce buffer. */ > *phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start), > *phys, size, dir, attrs); > - if (*phys == DMA_MAPPING_ERROR) > + if (*phys == SWIOTLB_MAP_ERROR) > return false; > > /* Ensure that the address returned is DMA'ble */ > -- > 2.20.0 >