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authorHarald Freudenberger <freude@linux.ibm.com>2019-02-22 17:24:11 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2019-03-06 09:34:03 +0100
commit01396a374c3d31bc5f8b693026cfa9a657319624 (patch)
treee1ae70d1fe7f5d1acfd509010e34919fadf9c9f5 /drivers/s390/crypto/ap_bus.c
parentcd479eccd2e057116d504852814402a1e68ead80 (diff)
s390/zcrypt: revisit ap device remove procedure
Working with the vfio-ap driver let to some revisit of the way how an ap (queue) device is removed from the driver. With the current implementation all the cleanup was done before the driver even got notified about the removal. Now the ap queue removal is done in 3 steps: 1) A preparation step, all ap messages within the queue are flushed and so the driver does 'receive' them. Also a new state AP_STATE_REMOVE assigned to the queue makes sure there are no new messages queued in. 2) Now the driver's remove function is invoked and the driver should do the job of cleaning up it's internal administration lists or whatever. After 2) is done it is guaranteed, that the driver is not invoked any more. On the other hand the driver has to make sure that the APQN is not accessed any more after step 2 is complete. 3) Now the ap bus code does the job of total cleanup of the APQN. A reset with zero is triggered and the state of the queue goes to AP_STATE_UNBOUND. After step 3) is complete, the ap queue has no pending messages and the APQN is cleared and so there are no requests and replies lingering around in the firmware queue for this APQN. Also the interrupts are disabled. After these remove steps the ap queue device may be assigned to another driver. Stress testing this remove/probe procedure showed a problem with the correct module reference counting. The actual receive of an reply in the driver is done asynchronous with completions. So with a driver change on an ap queue the message flush triggers completions but the threads waiting for the completions may run at a time where the queue already has the new driver assigned. So the module_put() at receive time needs to be done on the driver module which queued the ap message. This change is also part of this patch. Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'drivers/s390/crypto/ap_bus.c')
-rw-r--r--drivers/s390/crypto/ap_bus.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index e15816ff1265..033a1acabf48 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -810,11 +810,18 @@ static int ap_device_remove(struct device *dev)
struct ap_device *ap_dev = to_ap_dev(dev);
struct ap_driver *ap_drv = ap_dev->drv;
+ /* prepare ap queue device removal */
if (is_queue_dev(dev))
- ap_queue_remove(to_ap_queue(dev));
+ ap_queue_prepare_remove(to_ap_queue(dev));
+
+ /* driver's chance to clean up gracefully */
if (ap_drv->remove)
ap_drv->remove(ap_dev);
+ /* now do the ap queue device remove */
+ if (is_queue_dev(dev))
+ ap_queue_remove(to_ap_queue(dev));
+
/* Remove queue/card from list of active queues/cards */
spin_lock_bh(&ap_list_lock);
if (is_card_dev(dev))

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