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Mon, 22 Jun 2020 19:10:59 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05MIw6Y3075152; Mon, 22 Jun 2020 19:10:58 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 31sv7qkhdy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 22 Jun 2020 19:10:58 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 05MJAuEt010530; Mon, 22 Jun 2020 19:10:56 GMT Received: from [10.39.220.59] (/10.39.220.59) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 22 Jun 2020 19:10:56 +0000 Subject: Re: [RFC PATCH] xen/privcmd: Convert get_user_pages*() to pin_user_pages*() To: Souptick Joarder , John Hubbard Cc: Juergen Gross , sstabellini@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, paul@xen.org References: <1592363698-4266-1-git-send-email-jrdr.linux@gmail.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9660 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 suspectscore=0 mlxlogscore=999 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006220126 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9660 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 cotscore=-2147483648 lowpriorityscore=0 phishscore=0 bulkscore=0 clxscore=1015 impostorscore=0 malwarescore=0 priorityscore=1501 spamscore=0 mlxscore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006220126 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/22/20 2:52 PM, Souptick Joarder wrote: > > I read the code again. I think, this check is needed to handle a scenar= io when > lock_pages() return -ENOSPC. Better to keep this check. Let me post v2 = of this > RFC for a clear view. Actually, error handling seems to be somewhat broken here. If lock_pages() returns number of pinned pages then that's what we end up returning from privcmd_ioctl_dm_op(), all the way to user ioctl(). Which I don't think is right, we should return proper (negative) error. Do you mind fixing that we well? Then you should be able to avoid testing pages in a loop. -boris