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Wed, 24 Oct 2018 13:57:21 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w9ODvFj1025402 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 24 Oct 2018 13:57:15 GMT Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w9ODvEe8029090; Wed, 24 Oct 2018 13:57:14 GMT Received: from dhcp-burlington7-2nd-B-east-10-152-55-162.usdhcp.oraclecorp.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 24 Oct 2018 06:57:14 -0700 Subject: Re: [PATCH] xen-swiotlb: exchange memory with Xen only when pages are contiguous To: Konrad Rzeszutek Wilk , Joe Jin Cc: "DONGLI.ZHANG" , konrad@kernel.org, Christoph Helwig , John Sobecki , "xen-devel@lists.xenproject.org" , "linux-kernel@vger.kernel.org\"" References: <20181024130246.GA22616@localhost.localdomain> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181024130246.GA22616@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9055 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810240121 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/24/18 9:02 AM, Konrad Rzeszutek Wilk wrote: > On Tue, Oct 23, 2018 at 08:09:04PM -0700, Joe Jin wrote: >> Commit 4855c92dbb7 "xen-swiotlb: fix the check condition for >> xen_swiotlb_free_coherent" only fixed memory address check condition >> on xen_swiotlb_free_coherent(), when memory was not physically >> contiguous and tried to exchanged with Xen via >> xen_destroy_contiguous_region it will lead kernel panic. > s/it will lead/which lead to/? > >> The correct check condition should be memory is in DMA area and >> physically contiguous. > "The correct check condition to make Xen hypercall to revert the > memory back from its 32-bit pool is if it is: > 1) Above its DMA bit mask (for example 32-bit devices can only address > up to 4GB, and we may want 4GB+2K), and Is this "and' or 'or'? > 2) If it not physically contingous > > N.B. The logic in the code is inverted, which leads to all sorts of > confusions." I would, in fact, suggest to make the logic the same in both xen_swiotlb_alloc_coherent() and xen_swiotlb_free_coherent() to avoid this. This will involve swapping if and else in the former. > > Does that sound correct? > >> Thank you Boris for pointing it out. >> > Fixes: 4855c92dbb7 ("xen-sw..") ? > >> Signed-off-by: Joe Jin >> Cc: Konrad Rzeszutek Wilk >> Cc: Boris Ostrovsky > Reported-by: Boris Ostrovs... ? >> Cc: Christoph Helwig >> Cc: Dongli Zhang >> Cc: John Sobecki >> --- >> drivers/xen/swiotlb-xen.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c >> index f5c1af4ce9ab..aed92fa019f9 100644 >> --- a/drivers/xen/swiotlb-xen.c >> +++ b/drivers/xen/swiotlb-xen.c >> @@ -357,8 +357,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, >> /* Convert the size to actually allocated. */ >> size = 1UL << (order + XEN_PAGE_SHIFT); >> >> - if (((dev_addr + size - 1 <= dma_mask)) || >> - range_straddles_page_boundary(phys, size)) >> + if ((dev_addr + size - 1 <= dma_mask) && >> + !range_straddles_page_boundary(phys, size)) >> xen_destroy_contiguous_region(phys, order); I don't think this is right. if ((dev_addr + size - 1 > dma_mask) || range_straddles_page_boundary(phys, size)) No? -boris >> >> xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs); >> -- >> 2.17.1 (Apple Git-112) >>