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Thu, 14 Mar 2019 15:02:27 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2EF2QLQ007258 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 Mar 2019 15:02:26 GMT Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2EF2OPE016956; Thu, 14 Mar 2019 15:02:24 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 ; Thu, 14 Mar 2019 15:02:24 +0000 Subject: Re: [Xen-devel][PATCH] xen/netfront: Remove unneeded .resume callback To: Oleksandr Andrushchenko , netdev@vger.kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, jgross@suse.com, sstabellini@kernel.org, davem@davemloft.net Cc: Oleksandr Andrushchenko , Volodymyr Babchuk References: <20190314131749.25706-1-andr2000@gmail.com> <6205819a-af39-8cd8-db87-f3fe047ff064@gmail.com> 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/60.4.0 MIME-Version: 1.0 In-Reply-To: <6205819a-af39-8cd8-db87-f3fe047ff064@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9194 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 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=8.0.1-1810050000 definitions=main-1903140106 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/14/19 10:52 AM, Oleksandr Andrushchenko wrote: > On 3/14/19 4:47 PM, Boris Ostrovsky wrote: >> On 3/14/19 9:17 AM, Oleksandr Andrushchenko wrote: >>> From: Oleksandr Andrushchenko >>> >>> Currently on driver resume we remove all the network queues and >>> destroy shared Tx/Rx rings leaving the driver in its current state >>> and never signaling the backend of this frontend's state change. >>> This leads to the number of consequences: >>> - when frontend withdraws granted references to the rings etc. it >>> cannot >>>    be cleanly done as the backend still holds those (it was not told to >>>    free the resources) >>> - it is not possible to resume driver operation as all the >>> communication >>>    means with the backned were destroyed by the frontend, thus >>>    making the frontend appear to the guest OS as functional, but >>>    not really. >> >> What do you mean? Are you saying that after resume you lose >> connectivity? > Exactly, if you take a look at the .resume callback as it is now > what it does it destroys the rings etc. and never notifies the backend > of that, e.g. it stays in, say, connected state with communication > channels destroyed. It never goes into any other Xen bus state, so > there is > no way its state machine can help recovering. My tree is about a month old so perhaps there is some sort of regression but this certainly works for me. After resume netfront gets XenbusStateInitWait from backend which causes xennet_connect(). -boris