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Wed, 13 Jun 2018 22:03:23 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w5DM3M5o005548 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 13 Jun 2018 22:03:22 GMT Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w5DM3LOf027651; Wed, 13 Jun 2018 22:03:21 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, 13 Jun 2018 15:03:21 -0700 Subject: Re: [PATCH v3 9/9] xen/gntdev: Implement dma-buf import functionality To: Oleksandr Andrushchenko , Oleksandr Andrushchenko , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, jgross@suse.com, konrad.wilk@oracle.com Cc: daniel.vetter@intel.com, dongwon.kim@intel.com, matthew.d.roper@intel.com References: <20180612134200.17456-1-andr2000@gmail.com> <20180612134200.17456-10-andr2000@gmail.com> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 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=5900 definitions=8923 signatures=668702 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=627 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806130234 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/13/2018 05:04 AM, Oleksandr Andrushchenko wrote: > On 06/13/2018 06:14 AM, Boris Ostrovsky wrote: >> >> >> On 06/12/2018 09:42 AM, Oleksandr Andrushchenko wrote: >> >>>   int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 >>> fd) >>>   { >>> -    return -EINVAL; >>> +    struct gntdev_dmabuf *gntdev_dmabuf; >>> +    struct dma_buf_attachment *attach; >>> +    struct dma_buf *dma_buf; >>> + >>> +    gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd); >>> +    if (IS_ERR(gntdev_dmabuf)) >>> +        return PTR_ERR(gntdev_dmabuf); >>> + >>> +    pr_debug("Releasing DMA buffer with fd %d\n", fd); >>> + >>> +    attach = gntdev_dmabuf->u.imp.attach; >>> + >>> +    if (gntdev_dmabuf->u.imp.sgt) >>> +        dma_buf_unmap_attachment(attach, gntdev_dmabuf->u.imp.sgt, >>> +                     DMA_BIDIRECTIONAL); >>> +    dma_buf = attach->dmabuf; >>> +    dma_buf_detach(attach->dmabuf, attach); >>> +    dma_buf_put(dma_buf); >>> + >>> +    dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, >>> +                      gntdev_dmabuf->nr_pages); >> >> >> >> Should you first end foreign access, before doing anything? >> > I am rolling back in reverse order here, so I think we first need > to finish local activities with the buffer and then end foreign > access. Looking at gntdev_dmabuf_imp_to_refs(), the order is     dmabuf_imp_alloc_storage()     dma_buf_attach()     dma_buf_map_attachment()     dmabuf_imp_grant_foreign_access() Or was I looking at wrong place? -boris