[PATCH v2 5/8] s390: vfio-ap: wait for queue empty on queue reset

[Tony Krowiak <akrowiak@linux.ibm.com>]

Refactors the AP queue reset function to wait until the queue is empty
after the PQAP(ZAPQ) instruction is executed to zero out the queue as
required by the AP architecture.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 091804317c5e..31ce30ee784d 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -744,15 +744,44 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
 	return NOTIFY_OK;
 }
 
-static int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
-				    unsigned int retry)
+static void vfio_ap_mdev_wait_for_qempty(unsigned long apid, unsigned long apqi)
 {
 	struct ap_queue_status status;
+	ap_qid_t qid = AP_MKQID(apid, apqi);
+	int retry = 5;
+
+	do {
+		status = ap_tapq(qid, NULL);
+		switch (status.response_code) {
+		case AP_RESPONSE_NORMAL:
+			if (status.queue_empty)
+				return;
+			msleep(20);
+			break;
+		case AP_RESPONSE_RESET_IN_PROGRESS:
+		case AP_RESPONSE_BUSY:
+			msleep(20);
+			break;
+		default:
+			pr_warn("%s: tapq err %02x: 0x%04x may not be empty\n",
+				__func__, status.response_code, q->apqn);
+			return;
+		}
+	} while (--retry);
+}
+
+int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi)
+{
+	struct ap_queue_status status;
+	int retry = 5;
 
 	do {
 		status = ap_zapq(AP_MKQID(apid, apqi));
 		switch (status.response_code) {
 		case AP_RESPONSE_NORMAL:
+			vfio_ap_mdev_wait_for_qempty(apid, apqi);
+			return 0;
+		case AP_RESPONSE_DECONFIGURED:
 			return 0;
 		case AP_RESPONSE_RESET_IN_PROGRESS:
 		case AP_RESPONSE_BUSY:
@@ -778,7 +807,7 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
 			     matrix_mdev->matrix.apm_max + 1) {
 		for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
 				     matrix_mdev->matrix.aqm_max + 1) {
-			ret = vfio_ap_mdev_reset_queue(apid, apqi, 1);
+			ret = vfio_ap_mdev_reset_queue(apid, apqi);
 			/*
 			 * Regardless whether a queue turns out to be busy, or
 			 * is not operational, we need to continue resetting
-- 
2.7.4