5.4-stable patches

added patches:
	s390-virtio_ccw-don-t-allocate-assign-airqs-for-non-existing-queues.patch

diff --git a/queue-5.4/s390-virtio_ccw-don-t-allocate-assign-airqs-for-non-existing-queues.patch b/queue-5.4/s390-virtio_ccw-don-t-allocate-assign-airqs-for-non-existing-queues.patch
new file mode 100644 (file)
index 0000000..33e68ef
--- /dev/null
+++ b/queue-5.4/s390-virtio_ccw-don-t-allocate-assign-airqs-for-non-existing-queues.patch
@@ -0,0 +1,141 @@
+From 2ccd42b959aaf490333dbd3b9b102eaf295c036a Mon Sep 17 00:00:00 2001
+From: David Hildenbrand <david@redhat.com>
+Date: Wed, 2 Apr 2025 22:36:21 +0200
+Subject: s390/virtio_ccw: Don't allocate/assign airqs for non-existing queues
+
+From: David Hildenbrand <david@redhat.com>
+
+commit 2ccd42b959aaf490333dbd3b9b102eaf295c036a upstream.
+
+If we finds a vq without a name in our input array in
+virtio_ccw_find_vqs(), we treat it as "non-existing" and set the vq pointer
+to NULL; we will not call virtio_ccw_setup_vq() to allocate/setup a vq.
+
+Consequently, we create only a queue if it actually exists (name != NULL)
+and assign an incremental queue index to each such existing queue.
+
+However, in virtio_ccw_register_adapter_ind()->get_airq_indicator() we
+will not ignore these "non-existing queues", but instead assign an airq
+indicator to them.
+
+Besides never releasing them in virtio_ccw_drop_indicators() (because
+there is no virtqueue), the bigger issue seems to be that there will be a
+disagreement between the device and the Linux guest about the airq
+indicator to be used for notifying a queue, because the indicator bit
+for adapter I/O interrupt is derived from the queue index.
+
+The virtio spec states under "Setting Up Two-Stage Queue Indicators":
+
+       ... indicator contains the guest address of an area wherein the
+       indicators for the devices are contained, starting at bit_nr, one
+       bit per virtqueue of the device.
+
+And further in "Notification via Adapter I/O Interrupts":
+
+       For notifying the driver of virtqueue buffers, the device sets the
+       bit in the guest-provided indicator area at the corresponding
+       offset.
+
+For example, QEMU uses in virtio_ccw_notify() the queue index (passed as
+"vector") to select the relevant indicator bit. If a queue does not exist,
+it does not have a corresponding indicator bit assigned, because it
+effectively doesn't have a queue index.
+
+Using a virtio-balloon-ccw device under QEMU with free-page-hinting
+disabled ("free-page-hint=off") but free-page-reporting enabled
+("free-page-reporting=on") will result in free page reporting
+not working as expected: in the virtio_balloon driver, we'll be stuck
+forever in virtballoon_free_page_report()->wait_event(), because the
+waitqueue will not be woken up as the notification from the device is
+lost: it would use the wrong indicator bit.
+
+Free page reporting stops working and we get splats (when configured to
+detect hung wqs) like:
+
+ INFO: task kworker/1:3:463 blocked for more than 61 seconds.
+       Not tainted 6.14.0 #4
+ "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
+ task:kworker/1:3 [...]
+ Workqueue: events page_reporting_process
+ Call Trace:
+  [<000002f404e6dfb2>] __schedule+0x402/0x1640
+  [<000002f404e6f22e>] schedule+0x3e/0xe0
+  [<000002f3846a88fa>] virtballoon_free_page_report+0xaa/0x110 [virtio_balloon]
+  [<000002f40435c8a4>] page_reporting_process+0x2e4/0x740
+  [<000002f403fd3ee2>] process_one_work+0x1c2/0x400
+  [<000002f403fd4b96>] worker_thread+0x296/0x420
+  [<000002f403fe10b4>] kthread+0x124/0x290
+  [<000002f403f4e0dc>] __ret_from_fork+0x3c/0x60
+  [<000002f404e77272>] ret_from_fork+0xa/0x38
+
+There was recently a discussion [1] whether the "holes" should be
+treated differently again, effectively assigning also non-existing
+queues a queue index: that should also fix the issue, but requires other
+workarounds to not break existing setups.
+
+Let's fix it without affecting existing setups for now by properly ignoring
+the non-existing queues, so the indicator bits will match the queue
+indexes.
+
+[1] https://lore.kernel.org/all/cover.1720611677.git.mst@redhat.com/
+
+Fixes: a229989d975e ("virtio: don't allocate vqs when names[i] = NULL")
+Reported-by: Chandra Merla <cmerla@redhat.com>
+Cc: stable@vger.kernel.org
+Signed-off-by: David Hildenbrand <david@redhat.com>
+Tested-by: Thomas Huth <thuth@redhat.com>
+Reviewed-by: Thomas Huth <thuth@redhat.com>
+Reviewed-by: Cornelia Huck <cohuck@redhat.com>
+Acked-by: Michael S. Tsirkin <mst@redhat.com>
+Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
+Link: https://lore.kernel.org/r/20250402203621.940090-1-david@redhat.com
+Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
+Signed-off-by: David Hildenbrand <david@redhat.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/s390/virtio/virtio_ccw.c |   16 ++++++++++++----
+ 1 file changed, 12 insertions(+), 4 deletions(-)
+
+--- a/drivers/s390/virtio/virtio_ccw.c
++++ b/drivers/s390/virtio/virtio_ccw.c
+@@ -261,11 +261,17 @@ static struct airq_info *new_airq_info(i
+ static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs,
+                                       u64 *first, void **airq_info)
+ {
+-      int i, j;
++      int i, j, queue_idx, highest_queue_idx = -1;
+       struct airq_info *info;
+       unsigned long indicator_addr = 0;
+       unsigned long bit, flags;
+ 
++      /* Array entries without an actual queue pointer must be ignored. */
++      for (i = 0; i < nvqs; i++) {
++              if (vqs[i])
++                      highest_queue_idx++;
++      }
++
+       for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) {
+               mutex_lock(&airq_areas_lock);
+               if (!airq_areas[i])
+@@ -275,7 +281,7 @@ static unsigned long get_airq_indicator(
+               if (!info)
+                       return 0;
+               write_lock_irqsave(&info->lock, flags);
+-              bit = airq_iv_alloc(info->aiv, nvqs);
++              bit = airq_iv_alloc(info->aiv, highest_queue_idx + 1);
+               if (bit == -1UL) {
+                       /* Not enough vacancies. */
+                       write_unlock_irqrestore(&info->lock, flags);
+@@ -284,8 +290,10 @@ static unsigned long get_airq_indicator(
+               *first = bit;
+               *airq_info = info;
+               indicator_addr = (unsigned long)info->aiv->vector;
+-              for (j = 0; j < nvqs; j++) {
+-                      airq_iv_set_ptr(info->aiv, bit + j,
++              for (j = 0, queue_idx = 0; j < nvqs; j++) {
++                      if (!vqs[j])
++                              continue;
++                      airq_iv_set_ptr(info->aiv, bit + queue_idx++,
+                                       (unsigned long)vqs[j]);
+               }
+               write_unlock_irqrestore(&info->lock, flags);

diff --git a/queue-5.4/series b/queue-5.4/series
index 0a7183224f0262b4c9f0d8933fcb7dbcd2c4ca97..22eb8ad77735aee8b2af75285ddfbe97478328b6 100644 (file)
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -173,3 +173,4 @@ acpi-pptt-fix-coding-mistakes-in-a-couple-of-sizeof-.patch
 x86-bugs-don-t-fill-rsb-on-vmexit-with-eibrs-retpoli.patch
 scsi-pm80xx-set-phy_attached-to-zero-when-device-is-.patch
 md-raid1-add-check-for-missing-source-disk-in-proces.patch
+s390-virtio_ccw-don-t-allocate-assign-airqs-for-non-existing-queues.patch