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Mon, 3 Aug 2026 16:09:26 +0000 (GMT) From: Claudio Imbrenda To: pbonzini@redhat.com Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, borntraeger@de.ibm.com Subject: [GIT PULL v1 10/23] s390/vfio_ccw: Implement a crw lock Date: Mon, 3 Aug 2026 18:09:11 +0200 Message-ID: <20260803160924.236807-11-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260803160924.236807-1-imbrenda@linux.ibm.com> References: <20260803160924.236807-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=E6P9Y6dl c=1 sm=1 tr=0 ts=6a70bd3d cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=5HEjZEaU-qRc82GsN3sA:9 X-Proofpoint-ORIG-GUID: _9QgTDtVjBGB2hzLw2hQVaS4pYNvqN9q X-Proofpoint-GUID: _9QgTDtVjBGB2hzLw2hQVaS4pYNvqN9q X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDE0MSBTYWx0ZWRfX517u5EZmL7St UG95DAKstGAN9EJlbRo+SHH+rU78dSasJxDTWqq3qOVOfgLA3UdNL69JtlPpcZ3MpTG7hQMqmMD euPfdUBbpu/UXcV3I0AdHl4vfu++lLk= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDE0MSBTYWx0ZWRfX7lvpUhX92e/e DL0pbUOJgtKJ43UQIy61FLB8ae0WF+tctg95r26xdSjb0ODLWRkwA02iKmU7ab98i/5PA6NWraE TX5LTGJx6FwR83dod08JSK5kKtKg0to+OCN2I2STzS7SKzH6niSwlgNshTrlbdc6Xw7p2NDtkJG NhCq8q39maCXEKOKl0gXLmOi8yceGWQMMvSx73eqXLRrE/ml13tpXlPomw77+NabpY/Ta2HYC/X Y9D9qiThfNPFtRbsRr6qohj+ddvfyC9cwZzgBOn1OQvGZlHW2t5QmPAp5HmZHVmt2n+ZRr1fm/G Fjkx2aIb1gsR+RqlGWixw80ZWGxMXmOL776hSqxsGWmG1JDWZrCBVqVl/R4qjFdkybHdMFZT9Td e8Mb8YA2Y3IoV14tgMQuloS9QLzIeDgu2xgM/Yo+ZzoikMCn1QNpxt/YUK7CBfU3bafjyZuGBOP pc/ZOeq0zk229BLQosg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-03_03,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 priorityscore=1501 suspectscore=0 adultscore=0 spamscore=0 malwarescore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608030141 From: Eric Farman Unlike the channel_program struct, which covers synchronous I/O submissions and asynchronous interrupts, the CRW region relies exclusively on asynchronous events coming from hardware. Implement a lock to manage the list of those payloads, to ensure they are read cohesively. Fixes: 3f02cb2fd9d2 ("vfio-ccw: Wire up the CRW irq and CRW region") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato Reviewed-by: Farhan Ali Signed-off-by: Eric Farman Signed-off-by: Christian Borntraeger --- drivers/s390/cio/vfio_ccw_chp.c | 26 ++++++++++++++++---------- drivers/s390/cio/vfio_ccw_drv.c | 6 ++++++ drivers/s390/cio/vfio_ccw_ops.c | 4 ++++ drivers/s390/cio/vfio_ccw_private.h | 4 ++++ 4 files changed, 30 insertions(+), 10 deletions(-) diff --git a/drivers/s390/cio/vfio_ccw_chp.c b/drivers/s390/cio/vfio_ccw_chp.c index 9269b54f5cfd..7708eb4d6de0 100644 --- a/drivers/s390/cio/vfio_ccw_chp.c +++ b/drivers/s390/cio/vfio_ccw_chp.c @@ -93,18 +93,13 @@ static ssize_t vfio_ccw_crw_region_read(struct vfio_ccw_private *private, loff_t pos = *ppos & VFIO_CCW_OFFSET_MASK; struct ccw_crw_region *region; struct vfio_ccw_crw *crw; + unsigned long flags; int ret; if (pos + count > sizeof(*region)) return -EINVAL; mutex_lock(&private->io_mutex); - crw = list_first_entry_or_null(&private->crw, - struct vfio_ccw_crw, next); - - if (crw) - list_del(&crw->next); - if (i >= private->num_regions) { ret = -EINVAL; goto out; @@ -113,6 +108,16 @@ static ssize_t vfio_ccw_crw_region_read(struct vfio_ccw_private *private, i = array_index_nospec(i, private->num_regions); region = private->region[i].data; + spin_lock_irqsave(&private->crw_lock, flags); + crw = list_first_entry_or_null(&private->crw, + struct vfio_ccw_crw, next); + + if (crw) + list_del(&crw->next); + + /* Drop CRW lock while copying to userspace */ + spin_unlock_irqrestore(&private->crw_lock, flags); + if (crw) memcpy(®ion->crw, &crw->crw, sizeof(region->crw)); @@ -122,15 +127,16 @@ static ssize_t vfio_ccw_crw_region_read(struct vfio_ccw_private *private, ret = count; region->crw = 0; - -out: - mutex_unlock(&private->io_mutex); - kfree(crw); /* Notify the guest if more CRWs are on our queue */ + spin_lock_irqsave(&private->crw_lock, flags); if (!list_empty(&private->crw) && private->crw_trigger) eventfd_signal(private->crw_trigger); + spin_unlock_irqrestore(&private->crw_lock, flags); + +out: + mutex_unlock(&private->io_mutex); return ret; } diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index 757ff5b2556e..ab6b518cc353 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -118,11 +118,14 @@ void vfio_ccw_sch_io_todo(struct work_struct *work) void vfio_ccw_crw_todo(struct work_struct *work) { struct vfio_ccw_private *private; + unsigned long flags; private = container_of(work, struct vfio_ccw_private, crw_work); + spin_lock_irqsave(&private->crw_lock, flags); if (!list_empty(&private->crw) && private->crw_trigger) eventfd_signal(private->crw_trigger); + spin_unlock_irqrestore(&private->crw_lock, flags); } void vfio_ccw_notoper_todo(struct work_struct *work) @@ -286,6 +289,7 @@ static void vfio_ccw_queue_crw(struct vfio_ccw_private *private, unsigned int rsid) { struct vfio_ccw_crw *crw; + unsigned long flags; /* * If unable to allocate a CRW, just drop the event and @@ -303,7 +307,9 @@ static void vfio_ccw_queue_crw(struct vfio_ccw_private *private, crw->crw.erc = erc; crw->crw.rsid = rsid; + spin_lock_irqsave(&private->crw_lock, flags); list_add_tail(&crw->next, &private->crw); + spin_unlock_irqrestore(&private->crw_lock, flags); queue_work(vfio_ccw_work_q, &private->crw_work); } diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c index 1df6d649565b..5ce91285c7d5 100644 --- a/drivers/s390/cio/vfio_ccw_ops.c +++ b/drivers/s390/cio/vfio_ccw_ops.c @@ -55,6 +55,7 @@ static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev) 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); + spin_lock_init(&private->crw_lock); private->cp.guest_cp = kzalloc_objs(struct ccw1, CCWCHAIN_LEN_MAX); if (!private->cp.guest_cp) @@ -131,6 +132,7 @@ static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev) struct vfio_ccw_private *private = container_of(vdev, struct vfio_ccw_private, vdev); struct vfio_ccw_crw *crw, *temp; + unsigned long flags; /* * Ensure these work items are fully drained, so none can @@ -146,10 +148,12 @@ static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev) cancel_work_sync(&private->crw_work); flush_work(&private->notoper_work); + spin_lock_irqsave(&private->crw_lock, flags); list_for_each_entry_safe(crw, temp, &private->crw, next) { list_del(&crw->next); kfree(crw); } + spin_unlock_irqrestore(&private->crw_lock, flags); kmem_cache_free(vfio_ccw_crw_region, private->crw_region); kmem_cache_free(vfio_ccw_schib_region, private->schib_region); diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h index 739121116ab6..3bd0171d38d0 100644 --- a/drivers/s390/cio/vfio_ccw_private.h +++ b/drivers/s390/cio/vfio_ccw_private.h @@ -98,6 +98,8 @@ struct vfio_ccw_parent { * @cp: channel program for the current I/O operation * @irb: irb info received from interrupt * @scsw: scsw info + * @crw_lock: serialization of CRW list information + * @crw: list of Channel Report Word elements * @io_trigger: eventfd ctx for signaling userspace I/O results * @crw_trigger: eventfd ctx for signaling userspace CRW information * @req_trigger: eventfd ctx for signaling userspace to return device @@ -120,6 +122,8 @@ struct vfio_ccw_private { struct channel_program cp; struct irb irb; union scsw scsw; + + spinlock_t crw_lock; struct list_head crw; struct eventfd_ctx *io_trigger; -- 2.55.0