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FAILED: patch "[PATCH] s390/vfio_ccw: Implement a crw lock" failed to apply to 5.10-stable tree

PATCH In review [email protected] 3 participants 4 messages Aug 20 – Aug 28

Subsystems (4)
Stable branch s390 s390 common I/O layer s390 VFIO-CCW driver
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author maintainer
#0 lore raw

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 16b0798024c0e9117e395829ddbbe70981c79d9c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026082012-jam-hardly-84ee@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 16b0798024c0e9117e395829ddbbe70981c79d9c Mon Sep 17 00:00:00 2001
From: Eric Farman <[email protected]>
Date: Tue, 28 Jul 2026 05:30:22 +0200
Subject: [PATCH] s390/vfio_ccw: Implement a crw lock

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 [email protected]
Reviewed-by Matthew Rosato <[email protected]>
Reviewed-by Farhan Ali <[email protected]>
Signed-off-by Eric Farman <[email protected]>
Signed-off-by Christian Borntraeger <[email protected]>
drivers/s390/cio/vfio_ccw_chp.c +16 -10
index 9269b54f5cfd..7708eb4d6de0 100644
@@ -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(&region->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;
 }
drivers/s390/cio/vfio_ccw_drv.c +6 -0
index 757ff5b2556e..ab6b518cc353 100644
@@ -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);
 }
drivers/s390/cio/vfio_ccw_ops.c +4 -0
index 1df6d649565b..5ce91285c7d5 100644
@@ -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);
drivers/s390/cio/vfio_ccw_private.h +4 -0
index 739121116ab6..3bd0171d38d0 100644
@@ -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;
maintainer
#1 lore raw

PATCH 1/1 s390/vfio_ccw: Implement a crw lock

From: Eric Farman <[email protected]>

[ Upstream commit 16b0798024c0e9117e395829ddbbe70981c79d9c ]

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 [email protected]
Reviewed-by Matthew Rosato <[email protected]>
Reviewed-by Farhan Ali <[email protected]>
Signed-off-by Eric Farman <[email protected]>
Signed-off-by Christian Borntraeger <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/s390/cio/vfio_ccw_chp.c     | 16 +++++++++++-----
 drivers/s390/cio/vfio_ccw_drv.c     | 10 ++++++++++
 drivers/s390/cio/vfio_ccw_private.h |  4 ++++
 3 files changed, 25 insertions(+), 5 deletions(-)
drivers/s390/cio/vfio_ccw_chp.c +11 -5
index 13b26a1c79886..4fc493584a1e2 100644
@@ -84,19 +84,24 @@ 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);
+	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);
 
-	mutex_lock(&private->io_mutex);
-	region = private->region[i].data;
+	/* Drop CRW lock while copying to userspace */
+	spin_unlock_irqrestore(&private->crw_lock, flags);
 
 	if (crw)
 		memcpy(&region->crw, &crw->crw, sizeof(region->crw));

@@ -107,14 +112,15 @@ static ssize_t vfio_ccw_crw_region_read(struct vfio_ccw_private *private,
 		ret = count;
 
 	region->crw = 0;
-
-	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, 1);
+	spin_unlock_irqrestore(&private->crw_lock, flags);
+
+	mutex_unlock(&private->io_mutex);
 
 	return ret;
 }
drivers/s390/cio/vfio_ccw_drv.c +10 -0
index e3c1060b6056c..83993a1423d00 100644
@@ -119,11 +119,14 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 static 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, 1);
+	spin_unlock_irqrestore(&private->crw_lock, flags);
 }
 
 /*

@@ -207,6 +210,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 	INIT_LIST_HEAD(&private->crw);
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
 	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
+	spin_lock_init(&private->crw_lock);
 	atomic_set(&private->avail, 1);
 	private->state = VFIO_CCW_STATE_STANDBY;
 

@@ -238,13 +242,16 @@ static int vfio_ccw_sch_remove(struct subchannel *sch)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
 	struct vfio_ccw_crw *crw, *temp;
+	unsigned long flags;
 
 	vfio_ccw_sch_quiesce(sch);
 
+	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);
 
 	vfio_ccw_mdev_unreg(sch);
 

@@ -305,6 +312,7 @@ 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

@@ -322,7 +330,9 @@ 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);
 }
drivers/s390/cio/vfio_ccw_private.h +4 -0
index 8723156b29eac..38f470c2d26c3 100644
@@ -83,6 +83,8 @@ struct vfio_ccw_crw {
  * @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
  * @io_work: work for deferral process of I/O handling
  */

@@ -104,6 +106,8 @@ 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;
Signature · 1 line
2.53.0
#2 lore raw

Re: [PATCH 5.10.y] s390/vfio_ccw: Implement a crw lock

Quoted 162 lines · Sasha Levin

From: Eric Farman <[email protected]>

[ Upstream commit 16b0798024c0e9117e395829ddbbe70981c79d9c ]

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 [email protected]
Reviewed-by Matthew Rosato <[email protected]>
Reviewed-by Farhan Ali <[email protected]>
Signed-off-by Eric Farman <[email protected]>
Signed-off-by Christian Borntraeger <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/s390/cio/vfio_ccw_chp.c     | 16 +++++++++++-----
 drivers/s390/cio/vfio_ccw_drv.c     | 10 ++++++++++
 drivers/s390/cio/vfio_ccw_private.h |  4 ++++
 3 files changed, 25 insertions(+), 5 deletions(-)
drivers/s390/cio/vfio_ccw_chp.c +11 -5
index 13b26a1c79886..4fc493584a1e2 100644
@@ -84,19 +84,24 @@ 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);
+	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);
 
-	mutex_lock(&private->io_mutex);
-	region = private->region[i].data;
+	/* Drop CRW lock while copying to userspace */
+	spin_unlock_irqrestore(&private->crw_lock, flags);
 
 	if (crw)
 		memcpy(&region->crw, &crw->crw, sizeof(region->crw));

@@ -107,14 +112,15 @@ static ssize_t vfio_ccw_crw_region_read(struct vfio_ccw_private *private,
 		ret = count;
 
 	region->crw = 0;
-
-	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, 1);
+	spin_unlock_irqrestore(&private->crw_lock, flags);
+
+	mutex_unlock(&private->io_mutex);
 
 	return ret;
 }
drivers/s390/cio/vfio_ccw_drv.c +10 -0
index e3c1060b6056c..83993a1423d00 100644
@@ -119,11 +119,14 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 static 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, 1);
+	spin_unlock_irqrestore(&private->crw_lock, flags);
 }
 
 /*

@@ -207,6 +210,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 	INIT_LIST_HEAD(&private->crw);
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
 	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
+	spin_lock_init(&private->crw_lock);
 	atomic_set(&private->avail, 1);
 	private->state = VFIO_CCW_STATE_STANDBY;
 

@@ -238,13 +242,16 @@ static int vfio_ccw_sch_remove(struct subchannel *sch)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
 	struct vfio_ccw_crw *crw, *temp;
+	unsigned long flags;
 
 	vfio_ccw_sch_quiesce(sch);
 
+	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);
 
 	vfio_ccw_mdev_unreg(sch);
 

@@ -305,6 +312,7 @@ 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

@@ -322,7 +330,9 @@ 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);
 }
drivers/s390/cio/vfio_ccw_private.h +4 -0
index 8723156b29eac..38f470c2d26c3 100644
@@ -83,6 +83,8 @@ struct vfio_ccw_crw {
  * @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
  * @io_work: work for deferral process of I/O handling
  */

@@ -104,6 +106,8 @@ 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;
Signature · 1 line
2.53.0

Does not apply to the queue :(

maintainer
#3 lore raw

Re: [PATCH 5.10.y] s390/vfio_ccw: Implement a crw lock

Quoted 1 line

Does not apply to the queue :(

Right. It collided with 87d569cb35a5 ("s390/vfio_ccw: Cancel existing workqueues"), which was still only queued when I sent this. That has now shipped in v5.10.267, so I will rebase and resend.

Signature · 2 lines
Thanks,
Sasha