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Tue, 30 Jul 2019 14:06:01 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x6UDwCtO131102; Tue, 30 Jul 2019 14:06:01 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2u0xv876un-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 30 Jul 2019 14:06:01 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x6UE5sXI002501; Tue, 30 Jul 2019 14:05:54 GMT Received: from bostrovs-us.us.oracle.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 30 Jul 2019 07:05:54 -0700 Subject: Re: [Xen-devel] [PATCH v4 8/9] xen/gntdev.c: Convert to use vm_map_pages() To: Souptick Joarder , =?UTF-8?Q?Marek_Marczykowski-G=c3=b3recki?= Cc: Andrew Morton , Matthew Wilcox , Michal Hocko , Juergen Gross , Russell King - ARM Linux , robin.murphy@arm.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Linux-MM References: <20190215024830.GA26477@jordon-HP-15-Notebook-PC> <20190728180611.GA20589@mail-itl> <20190729133642.GQ1250@mail-itl> 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/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9334 signatures=668685 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=8.0.1-1906280000 definitions=main-1907300146 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9334 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=8.0.1-1906280000 definitions=main-1907300146 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/30/19 2:03 AM, Souptick Joarder wrote: > On Mon, Jul 29, 2019 at 7:06 PM Marek Marczykowski-Górecki > wrote: >> On Mon, Jul 29, 2019 at 02:02:54PM +0530, Souptick Joarder wrote: >>> On Mon, Jul 29, 2019 at 1:35 PM Souptick Joarder wrote: >>>> On Sun, Jul 28, 2019 at 11:36 PM Marek Marczykowski-Górecki >>>> wrote: >>>>> On Fri, Feb 15, 2019 at 08:18:31AM +0530, Souptick Joarder wrote: >>>>>> Convert to use vm_map_pages() to map range of kernel >>>>>> memory to user vma. >>>>>> >>>>>> map->count is passed to vm_map_pages() and internal API >>>>>> verify map->count against count ( count = vma_pages(vma)) >>>>>> for page array boundary overrun condition. >>>>> This commit breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages >>>>> will: >>>>> - use map->pages starting at vma->vm_pgoff instead of 0 >>>> The actual code ignores vma->vm_pgoff > 0 scenario and mapped >>>> the entire map->pages[i]. Why the entire map->pages[i] needs to be mapped >>>> if vma->vm_pgoff > 0 (in original code) ? >> vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's >> basically (ab)using this parameter for "which grant reference to map". >> >>>> are you referring to set vma->vm_pgoff = 0 irrespective of value passed >>>> from user space ? If yes, using vm_map_pages_zero() is an alternate >>>> option. >> Yes, that should work. > I prefer to use vm_map_pages_zero() to resolve both the issues. Alternatively > the patch can be reverted as you suggested. Let me know you opinion and wait > for feedback from others. > > Boris, would you like to give any feedback ? vm_map_pages_zero() looks good to me. Marek, does it work for you? -boris