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Mon, 27 Jul 2026 21:54:53 +0000 (GMT) Received: from [9.61.157.32] (unknown [9.61.157.32]) by smtpav04.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 27 Jul 2026 21:54:53 +0000 (GMT) Message-ID: <1819d316-62b9-48c7-abaa-f40681e22abf@linux.ibm.com> Date: Mon, 27 Jul 2026 17:54:52 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 08/10] s390/vfio_ccw: move cp cleanup out of not operational To: Eric Farman , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Halil Pasic , Christian Borntraeger , stable@vger.kernel.org References: <20260727192230.2715207-1-farman@linux.ibm.com> <20260727192230.2715207-9-farman@linux.ibm.com> From: Matthew Rosato Content-Language: en-US In-Reply-To: <20260727192230.2715207-9-farman@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI3MDE5NiBTYWx0ZWRfX1dq3HIHLJ5sv Pq8pKcr+HBidr4hO2o5gKXN+84JlTyhS4U2n0wjKmXbLlzFwKgOv/UOjesupIr12bKQAb0VpIwT Kp2Tduv4xs0eYonFDvoX7l9B8oVxRO8= X-Proofpoint-GUID: sq_oiCZzpLJ_NJS1Jx2YdNU_5lb3Jl2v X-Proofpoint-ORIG-GUID: sq_oiCZzpLJ_NJS1Jx2YdNU_5lb3Jl2v X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI3MDE5NiBTYWx0ZWRfX9V5IsByxDCpt +MV+LxF9eO/YTtEFmE3uXqZoCeEDTC605IUbsOu9LR5dd3PwvJJWdaJgZWBHkoDRXnp+ojgHk0a /p+JWmFGBobTYZZ+SFtYpX0KZX+K30kKl4ayy3unbN8qseQInTtwa2ocaxzhe10Nd7kb0OsmgG1 cYWL1bVJAxEHoYK2atk7XSXdMxGZL7vN3af/1BhUs8cVpK0gvHzIdmNatNWFCBfucw/fqJQSR8G iJK4ehtoaN9zQu9V0BsHKO5tFxzC/Yw/DMIszLgkjsOB5TkXzh1MsE7vtGLvlltFpluuhwjaLw3 ZySZ6FPJ1XnMWWH2ve1zmjUjVsZ5C5GCYHKzIQ9PFabNfVRyOpDOBdBMr15WLjDtqPXI1DladYL VKf4PEWBdkuDljjICKNduhR3s+GgoMvIL2XXvcH+GHSqhlQ31X7+hQw4tZa8/OWVPAPPbQI9y5l WY0M1xpQCBfwefi4AHg== X-Authority-Analysis: v=2.4 cv=X5Vi7mTe c=1 sm=1 tr=0 ts=6a67d3b0 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=2CkcZuEoo9mvoDp0OvwA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-27_06,2026-07-27_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 malwarescore=0 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607270196 On 7/27/26 3:22 PM, Eric Farman wrote: > The fsm_notoper() routine is called when the device has been > lost, and is (by definition) no longer operational. Since this > can happen asynchronously from the normal behavior of the > driver, the cleanup may happen when holding other locks > in the calling sequence (notably, the cio subchannel lock). > > Push the cleanup of the private->cp resources to a workqueue, > where it can be done out from under that lock sequence and > (soon) under its own serialization mechanism. This part of the commit message needs updating now that you are not introducing a cp_mutex. > > Fixes: 204b394a23ad ("vfio/ccw: Move FSM open/close to MDEV open/close") > Cc: stable@vger.kernel.org > Signed-off-by: Eric Farman > --- > drivers/s390/cio/vfio_ccw_drv.c | 9 +++++++++ > drivers/s390/cio/vfio_ccw_fsm.c | 3 +-- > drivers/s390/cio/vfio_ccw_ops.c | 3 +++ > drivers/s390/cio/vfio_ccw_private.h | 3 +++ > 4 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c > index 1a095085bc72..c197ad5ab580 100644 > --- a/drivers/s390/cio/vfio_ccw_drv.c > +++ b/drivers/s390/cio/vfio_ccw_drv.c > @@ -125,6 +125,15 @@ void vfio_ccw_crw_todo(struct work_struct *work) > eventfd_signal(private->crw_trigger); > } > > +void vfio_ccw_notoper_todo(struct work_struct *work) > +{ > + struct vfio_ccw_private *private; > + > + private = container_of(work, struct vfio_ccw_private, notoper_work); > + > + cp_free(&private->cp); > +} > + > /* > * Css driver callbacks > */ > diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c > index 4d7988ea47ef..4d47a3c7b9a0 100644 > --- a/drivers/s390/cio/vfio_ccw_fsm.c > +++ b/drivers/s390/cio/vfio_ccw_fsm.c > @@ -170,8 +170,7 @@ static void fsm_notoper(struct vfio_ccw_private *private, > css_sched_sch_todo(sch, SCH_TODO_UNREG); > private->state = VFIO_CCW_STATE_NOT_OPER; > > - /* This is usually handled during CLOSE event */ > - cp_free(&private->cp); > + queue_work(vfio_ccw_work_q, &private->notoper_work); > } > > /* > diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c > index bd488e40e153..8ec6b175d991 100644 > --- a/drivers/s390/cio/vfio_ccw_ops.c > +++ b/drivers/s390/cio/vfio_ccw_ops.c > @@ -54,6 +54,7 @@ static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev) > INIT_LIST_HEAD(&private->crw); > INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo); > INIT_WORK(&private->crw_work, vfio_ccw_crw_todo); > + INIT_WORK(&private->notoper_work, vfio_ccw_notoper_todo); > > private->cp.guest_cp = kzalloc_objs(struct ccw1, CCWCHAIN_LEN_MAX); > if (!private->cp.guest_cp) > @@ -139,6 +140,7 @@ static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev) > /* Should be empty, but just in case */ > cancel_work_sync(&private->io_work); > cancel_work_sync(&private->crw_work); > + cancel_work_sync(&private->notoper_work); Sashiko mentions (and I agree) that you can accidentally leak the cp resources if you manage to cancel the pending notoper_work before it runs. Since you are not running on a workqueue thread, it should be OK to flush instead to make sure that the pending item is executed. A subsequent cancel should not be necessary, since we know that only 1 instance of vfio_ccw_notoper_todo() will ever be queued because we queue it on the first time the device goes NOT_OPER. Based on the FSM, once the device goes NOT_OPER, subsequent transitions into NOT_OPER are treated as a NOP and there is no way to transition to a different state other than NOT_OPER until the device is released, so you can't go from NOT_OPER->x->NOT_OPER. Would probably be good to include a (less verbose) comment to that effect along with the flush. > > kmem_cache_free(vfio_ccw_crw_region, private->crw_region); > kmem_cache_free(vfio_ccw_schib_region, private->schib_region); > @@ -209,6 +211,7 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev) > > cancel_work_sync(&private->io_work); > cancel_work_sync(&private->crw_work); > + cancel_work_sync(&private->notoper_work); > > vfio_ccw_unregister_dev_regions(private); > } > diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h > index 0501d4bbcdbd..e2256402b089 100644 > --- a/drivers/s390/cio/vfio_ccw_private.h > +++ b/drivers/s390/cio/vfio_ccw_private.h > @@ -102,6 +102,7 @@ struct vfio_ccw_parent { > * @req_trigger: eventfd ctx for signaling userspace to return device > * @io_work: work for deferral process of I/O handling > * @crw_work: work for deferral process of CRW handling > + * @notoper_work: work for deferred processing in not-operational state > */ > struct vfio_ccw_private { > struct vfio_device vdev; > @@ -125,11 +126,13 @@ struct vfio_ccw_private { > struct eventfd_ctx *req_trigger; > struct work_struct io_work; > struct work_struct crw_work; > + struct work_struct notoper_work; > } __aligned(8); > > int vfio_ccw_sch_quiesce(struct subchannel *sch); > void vfio_ccw_sch_io_todo(struct work_struct *work); > void vfio_ccw_crw_todo(struct work_struct *work); > +void vfio_ccw_notoper_todo(struct work_struct *work); > > extern struct mdev_driver vfio_ccw_mdev_driver; >