From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Fri, 16 Nov 2007 13:58:57 +0100
Subject: [s390] qdio: output queue stall on FCP and net devs
Message-id: 20071116125857.GU6053@redhat.com
O-Subject: [RHEL5 U2 PATCH 13/14] s390 - qdio: output queue stall on FCP and network devices
Bugzilla: 354871

Description
============

When running QIOASSIST enabled qdio devices in a z/VM
environment, the output queue for such devices stalls in
heavy workload situations. When SQBS and EQBS
instructions return CCQ=96, qdio did not reissue the
instruction again with the register settings done by
millicode, but processed the returned qdio buffer.
Solution: qdio now reissues the instruction once again on CCQ=96,
as already done for CCQ=97.

Bugzilla
=========

BZ 354871
https://bugzilla.redhat.com/show_bug.cgi?id=354871

Upstream status of the patch:
=============================
Patch included in git as commit 6cbed91ab78e750eef2dacb75bd51bd63792fd07

Test status:
============
Kernel with patch was built and successfully tested

Please ACK.

With best regards,

Hans

diff --git a/drivers/s390/cio/qdio.c b/drivers/s390/cio/qdio.c
index 844e5f3..fbb2b54 100644
--- a/drivers/s390/cio/qdio.c
+++ b/drivers/s390/cio/qdio.c
@@ -166,9 +166,9 @@ qdio_check_ccq(struct qdio_q *q, unsigned int ccq)
 {
 	char dbf_text[15];
 
-	if (ccq == 0 || ccq == 32 || ccq == 96)
+	if (ccq == 0 || ccq == 32)
 		return 0;
-	if (ccq == 97)
+	if (ccq == 96 || ccq == 97)
 		return 1;
 	/*notify devices immediately*/
 	sprintf(dbf_text,"%d", ccq);
@@ -194,6 +194,8 @@ qdio_do_eqbs(struct qdio_q *q, unsigned char *state,
 again:
 	ccq = do_eqbs(irq->sch_token, state, q_no, start, cnt);
 	rc = qdio_check_ccq(q, ccq);
+	if ((ccq == 96) && (tmp_cnt != *cnt))
+		rc = 0;
 	if (rc == 1) {
 		QDIO_DBF_TEXT5(1,trace,"eqAGAIN");
 		goto again;