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[23.128.96.18]) by mx.google.com with ESMTP id s9si314280edh.243.2020.08.19.17.29.41; Wed, 19 Aug 2020 17:30:05 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2020-01-29 header.b=oQ8GMOKQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726703AbgHTA2s (ORCPT + 99 others); Wed, 19 Aug 2020 20:28:48 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:33084 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726609AbgHTA2r (ORCPT ); Wed, 19 Aug 2020 20:28:47 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 07K0SagY005582; Thu, 20 Aug 2020 00:28:36 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=vel+smFQdJIkcUoSS2CWHtxEjDOkisx508rK5q+tszw=; b=oQ8GMOKQj3nvNCXllKq06pgp7nljxgmLsZOFUAWIQZjrZCSZ6GuzO46lvWP41EnYuSPY cw2lDQeua2PlKOPdh7qgqR9YYkVXNM08W/bWsh6dkRJauc5ne8LYXcbgYPC/2Gk8zQFx YLZ2wkT0owFDf0ms5SIcnNtNu8IeUn5pL5alkfGKzfVu6MDwNymJjIb1cZLMCRYvYOxG 4SCYSFq45I84YuUpOyQX144qCbnDn5XL5tepHZaFvFaUomiFuzmxn9iEwt6KiO+RzkFP +zW2pCjWOanPgMZJTr4x+Q6khCteM45RfV51037sAwOVwv6+eezPIN67qIvbI2sH9Tfs lQ== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 32x74rdfx5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 20 Aug 2020 00:28:36 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 07K0NpLD031106; Thu, 20 Aug 2020 00:26:35 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 330pvmprrc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 20 Aug 2020 00:26:35 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 07K0QYdT014310; Thu, 20 Aug 2020 00:26:34 GMT Received: from [10.74.109.193] (/10.74.109.193) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 19 Aug 2020 17:26:34 -0700 Subject: Re: [RFC PATCH] xen/gntdev.c: Convert get_user_pages*() to pin_user_pages*() To: Souptick Joarder , jgross@suse.com, sstabellini@kernel.org Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, John Hubbard References: <1597725140-8310-1-git-send-email-jrdr.linux@gmail.com> From: boris.ostrovsky@oracle.com Organization: Oracle Corporation Message-ID: <82366a3d-db55-68eb-7f29-935b511dace4@oracle.com> Date: Wed, 19 Aug 2020 20:26:31 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <1597725140-8310-1-git-send-email-jrdr.linux@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9718 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 phishscore=0 malwarescore=0 adultscore=0 bulkscore=0 suspectscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008200001 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9718 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 impostorscore=0 mlxlogscore=999 priorityscore=1501 phishscore=0 spamscore=0 mlxscore=0 adultscore=0 suspectscore=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008200002 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/18/20 12:32 AM, Souptick Joarder wrote: > In 2019, we introduced pin_user_pages*() and now we are converting > get_user_pages*() to the new API as appropriate. [1] & [2] could > be referred for more information. This is case 5 as per document [1]. > > [1] Documentation/core-api/pin_user_pages.rst > > [2] "Explicit pinning of user-space pages": > https://lwn.net/Articles/807108/ > > Signed-off-by: Souptick Joarder > Cc: John Hubbard > --- > drivers/xen/gntdev.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 64a9025a..e480509 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -730,7 +730,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, > unsigned long xen_pfn; > int ret; > > - ret = get_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); > + ret = pin_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); > if (ret < 0) > return ret; > > @@ -744,10 +744,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, > > static void gntdev_put_pages(struct gntdev_copy_batch *batch) > { > - unsigned int i; > - > - for (i = 0; i < batch->nr_pages; i++) > - put_page(batch->pages[i]); > + unpin_user_pages(batch->pages, batch->nr_pages); There seems to be a bug in the original code (just like there was in privcmd.c that you fixed earlier) --- when gntdev_get_page() is called with writeable=true then the page needs to be marked dirty before being put. You can add a `bool writeable` to gntdev_copy_batch and set it in gntdev_grant_copy_seg() (and drop `writeable` argument to gntdev_get_page()) and then, based on batch->writeable, use either unpin_user_pages() or unpin_user_pages_dirty_lock(). (But to fix this in stable branches please make first patch call set_page_dirty_lock() for each page like you did in previous series) -boris > batch->nr_pages = 0; > } >