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Wed, 19 Jun 2019 14:26:58 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5JEQTAe194064; Wed, 19 Jun 2019 14:26:57 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 2t77ynvp68-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 19 Jun 2019 14:26:57 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x5JEQm9v015046; Wed, 19 Jun 2019 14:26:48 GMT Received: from char.us.oracle.com (/10.152.32.25) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 19 Jun 2019 07:26:47 -0700 Received: by char.us.oracle.com (Postfix, from userid 1000) id 434C96A0136; Wed, 19 Jun 2019 10:28:12 -0400 (EDT) Date: Wed, 19 Jun 2019 10:28:12 -0400 From: Konrad Rzeszutek Wilk To: Stefano Stabellini Cc: Arnd Bergmann , Christoph Hellwig , Marek Szyprowski , Jesper Dangaard Brouer , Boris Ostrovsky , Juergen Gross , 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] swiotlb: fix phys_addr_t overflow warning Message-ID: <20190619142812.GM10432@char.us.oracle.com> References: <20190617132946.2817440-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9292 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906190118 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9292 signatures=668687 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-1906190118 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 17, 2019 at 09:13:16AM -0700, Stefano Stabellini wrote: > On Mon, 17 Jun 2019, Arnd Bergmann wrote: > > On architectures that have a larger dma_addr_t than phys_addr_t, > > the swiotlb_tbl_map_single() function truncates its return code > > in the failure path, making it impossible to identify the error > > later, as we compare to the original value: > > > > kernel/dma/swiotlb.c:551:9: error: implicit conversion from 'dma_addr_t' (aka 'unsigned long long') to 'phys_addr_t' (aka 'unsigned int') changes value from 18446744073709551615 to 4294967295 [-Werror,-Wconstant-conversion] > > return DMA_MAPPING_ERROR; > > > > Use an explicit typecast here to convert it to the narrower type, > > and use the same expression in the error handling later. > > > > Fixes: b907e20508d0 ("swiotlb: remove SWIOTLB_MAP_ERROR") > > Signed-off-by: Arnd Bergmann > > Acked-by: Stefano Stabellini queued. > > > > --- > > I still think that reverting the original commit would have > > provided clearer semantics for this corner case, but at least > > this patch restores the correct behavior. > > --- > > drivers/xen/swiotlb-xen.c | 2 +- > > kernel/dma/swiotlb.c | 4 ++-- > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > > index d53f3493a6b9..cfbe46785a3b 100644 > > --- a/drivers/xen/swiotlb-xen.c > > +++ b/drivers/xen/swiotlb-xen.c > > @@ -402,7 +402,7 @@ 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 == (phys_addr_t)DMA_MAPPING_ERROR) > > return DMA_MAPPING_ERROR; > > > > dev_addr = xen_phys_to_bus(map); > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > > index e906ef2e6315..a3be651973ad 100644 > > --- a/kernel/dma/swiotlb.c > > +++ b/kernel/dma/swiotlb.c > > @@ -548,7 +548,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, > > if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit()) > > dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n", > > size, io_tlb_nslabs, tmp_io_tlb_used); > > - return DMA_MAPPING_ERROR; > > + return (phys_addr_t)DMA_MAPPING_ERROR; > > found: > > io_tlb_used += nslots; > > spin_unlock_irqrestore(&io_tlb_lock, flags); > > @@ -666,7 +666,7 @@ 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 == (phys_addr_t)DMA_MAPPING_ERROR) > > return false; > > > > /* Ensure that the address returned is DMA'ble */ > > -- > > 2.20.0 > >