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Thu, 16 Jun 2022 15:35:19 +0000 (GMT) Received: from [9.211.56.136] (unknown [9.211.56.136]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 16 Jun 2022 15:35:18 +0000 (GMT) Message-ID: <6d6451d0-68cb-4dcf-c6c7-7480e6ae8e78@linux.ibm.com> Date: Thu, 16 Jun 2022 11:35:18 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v2 03/10] vfio/ccw: Do not change FSM state in subchannel event Content-Language: en-US To: Eric Farman Cc: Jason Gunthorpe , Alex Williamson , Cornelia Huck , Halil Pasic , kvm@vger.kernel.org, linux-s390@vger.kernel.org References: <20220615203318.3830778-1-farman@linux.ibm.com> <20220615203318.3830778-4-farman@linux.ibm.com> From: Matthew Rosato In-Reply-To: <20220615203318.3830778-4-farman@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: abj_eNAyQwQugUHqoD9JCTJtJMLeTDFH X-Proofpoint-ORIG-GUID: RjVQ7gMg6mKwn3IrNMEBTxboBA06mQRw X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-06-16_11,2022-06-16_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 clxscore=1015 spamscore=0 phishscore=0 mlxlogscore=658 malwarescore=0 adultscore=0 mlxscore=0 bulkscore=0 impostorscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2206160060 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 6/15/22 4:33 PM, Eric Farman wrote: > The routine vfio_ccw_sch_event() is tasked with handling subchannel events, > specifically machine checks, on behalf of vfio-ccw. It correctly calls > cio_update_schib(), and if that fails (meaning the subchannel is gone) > it makes an FSM event call to mark the subchannel Not Operational. > > If that worked, however, then it decides that if the FSM state was already > Not Operational (implying the subchannel just came back), then it should > simply change the FSM to partially- or fully-open. > > Remove this trickery, since a subchannel returning will require more > probing than simply "oh all is well again" to ensure it works correctly. > > Fixes: bbe37e4cb8970 ("vfio: ccw: introduce a finite state machine") > Signed-off-by: Eric Farman So, I agree that this code does not belong here and should be removed -- if the subchannel just came back, we can't assume it's even the same device. We'd better just leave it NOT_OPER for this weird window for now. So... Reviewed-by: Matthew Rosato But I also wonder if more work could be done from vfio_ccw_sch_event based upon whats in the schib, like what io_subchannel_sch_event does (e.g. detecting if a reprobe of the device is necessary). We should probably take a closer look here for potential follow-ups. > --- > drivers/s390/cio/vfio_ccw_drv.c | 14 +++----------- > 1 file changed, 3 insertions(+), 11 deletions(-) > > diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c > index 179eb614fa5b..279ad2161f17 100644 > --- a/drivers/s390/cio/vfio_ccw_drv.c > +++ b/drivers/s390/cio/vfio_ccw_drv.c > @@ -301,19 +301,11 @@ static int vfio_ccw_sch_event(struct subchannel *sch, int process) > if (work_pending(&sch->todo_work)) > goto out_unlock; > > - if (cio_update_schib(sch)) { > - vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER); > - rc = 0; > - goto out_unlock; > - } > - > - private = dev_get_drvdata(&sch->dev); > - if (private->state == VFIO_CCW_STATE_NOT_OPER) { > - private->state = private->mdev ? VFIO_CCW_STATE_IDLE : > - VFIO_CCW_STATE_STANDBY; > - } > rc = 0; > > + if (cio_update_schib(sch)) > + vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER); > + > out_unlock: > spin_unlock_irqrestore(sch->lock, flags); >