[PATCH net 0/4] s390/qeth: fixes 2020-11-20

[PATCH net 0/4] s390/qeth: fixes 2020-11-20

[Julian Wiedmann]

Hi Jakub,

please apply the following patch series to netdev's net tree.

This brings several fixes for qeth's af_iucv-specific code paths.

Also one fix by Alexandra for the recently added BR_LEARNING_SYNC
support. We want to trust the feature indication bit, so that HW can
mask it out if there's any issues on their end.

Thanks,
Julian

Alexandra Winter (1):
  s390/qeth: Remove pnso workaround

Julian Wiedmann (3):
  s390/qeth: make af_iucv TX notification call more robust
  s390/qeth: fix af_iucv notification race
  s390/qeth: fix tear down of async TX buffers

 drivers/s390/net/qeth_core.h      |  9 ++--
 drivers/s390/net/qeth_core_main.c | 82 ++++++++++++++++++++-----------
 drivers/s390/net/qeth_l2_main.c   | 18 +------
 3 files changed, 62 insertions(+), 47 deletions(-)

-- 
2.17.1

[PATCH net 1/4] s390/qeth: Remove pnso workaround

[Julian Wiedmann]

From: Alexandra Winter <wintera@linux.ibm.com>

Remove workaround that supported early hardware implementations
of PNSO OC3. Rely on the 'enarf' feature bit instead.

Fixes: fa115adff2c1 ("s390/qeth: Detect PNSO OC3 capability")
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Julian Wiedmann <jwi@linux.ibm.com>
[jwi: use logical instead of bit-wise AND]
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
 drivers/s390/net/qeth_l2_main.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 28f6dda95736..79939ba5d523 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -985,32 +985,19 @@ static void qeth_l2_setup_bridgeport_attrs(struct qeth_card *card)
  *	change notification' and thus can support the learning_sync bridgeport
  *	attribute
  *	@card: qeth_card structure pointer
- *
- *	This is a destructive test and must be called before dev2br or
- *	bridgeport address notification is enabled!
  */
 static void qeth_l2_detect_dev2br_support(struct qeth_card *card)
 {
 	struct qeth_priv *priv = netdev_priv(card->dev);
 	bool dev2br_supported;
-	int rc;
 
 	QETH_CARD_TEXT(card, 2, "d2brsup");
 	if (!IS_IQD(card))
 		return;
 
 	/* dev2br requires valid cssid,iid,chid */
-	if (!card->info.ids_valid) {
-		dev2br_supported = false;
-	} else if (css_general_characteristics.enarf) {
-		dev2br_supported = true;
-	} else {
-		/* Old machines don't have the feature bit:
-		 * Probe by testing whether a disable succeeds
-		 */
-		rc = qeth_l2_pnso(card, PNSO_OC_NET_ADDR_INFO, 0, NULL, NULL);
-		dev2br_supported = !rc;
-	}
+	dev2br_supported = card->info.ids_valid &&
+			   css_general_characteristics.enarf;
 	QETH_CARD_TEXT_(card, 2, "D2Bsup%02x", dev2br_supported);
 
 	if (dev2br_supported)
@@ -2233,7 +2220,6 @@ static int qeth_l2_set_online(struct qeth_card *card, bool carrier_ok)
 	struct net_device *dev = card->dev;
 	int rc = 0;
 
-	/* query before bridgeport_notification may be enabled */
 	qeth_l2_detect_dev2br_support(card);
 
 	mutex_lock(&card->sbp_lock);
-- 
2.17.1

[PATCH net 2/4] s390/qeth: make af_iucv TX notification call more robust

[Julian Wiedmann]

Calling into socket code is ugly already, at least check whether we are
dealing with the expected sk_family. Only looking at skb->protocol is
bound to cause troubles (consider eg. af_packet).

Fixes: b333293058aa ("qeth: add support for af_iucv HiperSockets transport")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
 drivers/s390/net/qeth_core_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 93c9b30ab17a..715f440bdc7c 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -33,6 +33,7 @@
 
 #include <net/iucv/af_iucv.h>
 #include <net/dsfield.h>
+#include <net/sock.h>
 
 #include <asm/ebcdic.h>
 #include <asm/chpid.h>
@@ -1405,7 +1406,7 @@ static void qeth_notify_skbs(struct qeth_qdio_out_q *q,
 	skb_queue_walk(&buf->skb_list, skb) {
 		QETH_CARD_TEXT_(q->card, 5, "skbn%d", notification);
 		QETH_CARD_TEXT_(q->card, 5, "%lx", (long) skb);
-		if (skb->protocol == htons(ETH_P_AF_IUCV) && skb->sk)
+		if (skb->sk && skb->sk->sk_family == PF_IUCV)
 			iucv_sk(skb->sk)->sk_txnotify(skb, notification);
 	}
 }
-- 
2.17.1

[PATCH net 3/4] s390/qeth: fix af_iucv notification race

[Julian Wiedmann]

The two expected notification sequences are
1. TX_NOTIFY_PENDING with a subsequent TX_NOTIFY_DELAYED_*, when
   our TX completion code first observed the pending TX and the QAOB
   then completes at a later time; or
2. TX_NOTIFY_OK, when qeth_qdio_handle_aob() picked up the QAOB
   completion before our TX completion code even noticed that the TX
   was pending.

But as qeth_iqd_tx_complete() and qeth_qdio_handle_aob() can run
concurrently, we may end up with a race that results in a sequence of
TX_NOTIFY_DELAYED_* followed by TX_NOTIFY_PENDING. Which would confuse
the af_iucv code in its tracking of pending transmits.

Rework the notification code, so that qeth_qdio_handle_aob() defers its
notification if the TX completion code is still active.

Fixes: b333293058aa ("qeth: add support for af_iucv HiperSockets transport")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
 drivers/s390/net/qeth_core.h      |  9 ++--
 drivers/s390/net/qeth_core_main.c | 73 ++++++++++++++++++++++---------
 2 files changed, 58 insertions(+), 24 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index f73b4756ed5e..b235393e091c 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -417,10 +417,13 @@ enum qeth_qdio_out_buffer_state {
 	QETH_QDIO_BUF_EMPTY,
 	/* Filled by driver; owned by hardware in order to be sent. */
 	QETH_QDIO_BUF_PRIMED,
-	/* Identified to be pending in TPQ. */
+	/* Discovered by the TX completion code: */
 	QETH_QDIO_BUF_PENDING,
-	/* Found in completion queue. */
-	QETH_QDIO_BUF_IN_CQ,
+	/* Finished by the TX completion code: */
+	QETH_QDIO_BUF_NEED_QAOB,
+	/* Received QAOB notification on CQ: */
+	QETH_QDIO_BUF_QAOB_OK,
+	QETH_QDIO_BUF_QAOB_ERROR,
 	/* Handled via transfer pending / completion queue. */
 	QETH_QDIO_BUF_HANDLED_DELAYED,
 };
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 715f440bdc7c..48f9e4a027bf 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -511,6 +511,7 @@ static void qeth_cleanup_handled_pending(struct qeth_qdio_out_q *q, int bidx,
 static void qeth_qdio_handle_aob(struct qeth_card *card,
 				 unsigned long phys_aob_addr)
 {
+	enum qeth_qdio_out_buffer_state new_state = QETH_QDIO_BUF_QAOB_OK;
 	struct qaob *aob;
 	struct qeth_qdio_out_buffer *buffer;
 	enum iucv_tx_notify notification;
@@ -522,22 +523,6 @@ static void qeth_qdio_handle_aob(struct qeth_card *card,
 	buffer = (struct qeth_qdio_out_buffer *) aob->user1;
 	QETH_CARD_TEXT_(card, 5, "%lx", aob->user1);
 
-	if (atomic_cmpxchg(&buffer->state, QETH_QDIO_BUF_PRIMED,
-			   QETH_QDIO_BUF_IN_CQ) == QETH_QDIO_BUF_PRIMED) {
-		notification = TX_NOTIFY_OK;
-	} else {
-		WARN_ON_ONCE(atomic_read(&buffer->state) !=
-							QETH_QDIO_BUF_PENDING);
-		atomic_set(&buffer->state, QETH_QDIO_BUF_IN_CQ);
-		notification = TX_NOTIFY_DELAYED_OK;
-	}
-
-	if (aob->aorc != 0)  {
-		QETH_CARD_TEXT_(card, 2, "aorc%02X", aob->aorc);
-		notification = qeth_compute_cq_notification(aob->aorc, 1);
-	}
-	qeth_notify_skbs(buffer->q, buffer, notification);
-
 	/* Free dangling allocations. The attached skbs are handled by
 	 * qeth_cleanup_handled_pending().
 	 */
@@ -549,7 +534,33 @@ static void qeth_qdio_handle_aob(struct qeth_card *card,
 		if (data && buffer->is_header[i])
 			kmem_cache_free(qeth_core_header_cache, data);
 	}
-	atomic_set(&buffer->state, QETH_QDIO_BUF_HANDLED_DELAYED);
+
+	if (aob->aorc) {
+		QETH_CARD_TEXT_(card, 2, "aorc%02X", aob->aorc);
+		new_state = QETH_QDIO_BUF_QAOB_ERROR;
+	}
+
+	switch (atomic_xchg(&buffer->state, new_state)) {
+	case QETH_QDIO_BUF_PRIMED:
+		/* Faster than TX completion code. */
+		notification = qeth_compute_cq_notification(aob->aorc, 0);
+		qeth_notify_skbs(buffer->q, buffer, notification);
+		atomic_set(&buffer->state, QETH_QDIO_BUF_HANDLED_DELAYED);
+		break;
+	case QETH_QDIO_BUF_PENDING:
+		/* TX completion code is active and will handle the async
+		 * completion for us.
+		 */
+		break;
+	case QETH_QDIO_BUF_NEED_QAOB:
+		/* TX completion code is already finished. */
+		notification = qeth_compute_cq_notification(aob->aorc, 1);
+		qeth_notify_skbs(buffer->q, buffer, notification);
+		atomic_set(&buffer->state, QETH_QDIO_BUF_HANDLED_DELAYED);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+	}
 
 	qdio_release_aob(aob);
 }
@@ -1417,9 +1428,6 @@ static void qeth_tx_complete_buf(struct qeth_qdio_out_buffer *buf, bool error,
 	struct qeth_qdio_out_q *queue = buf->q;
 	struct sk_buff *skb;
 
-	/* release may never happen from within CQ tasklet scope */
-	WARN_ON_ONCE(atomic_read(&buf->state) == QETH_QDIO_BUF_IN_CQ);
-
 	if (atomic_read(&buf->state) == QETH_QDIO_BUF_PENDING)
 		qeth_notify_skbs(queue, buf, TX_NOTIFY_GENERALERROR);
 
@@ -5870,9 +5878,32 @@ static void qeth_iqd_tx_complete(struct qeth_qdio_out_q *queue,
 
 		if (atomic_cmpxchg(&buffer->state, QETH_QDIO_BUF_PRIMED,
 						   QETH_QDIO_BUF_PENDING) ==
-		    QETH_QDIO_BUF_PRIMED)
+		    QETH_QDIO_BUF_PRIMED) {
 			qeth_notify_skbs(queue, buffer, TX_NOTIFY_PENDING);
 
+			/* Handle race with qeth_qdio_handle_aob(): */
+			switch (atomic_xchg(&buffer->state,
+					    QETH_QDIO_BUF_NEED_QAOB)) {
+			case QETH_QDIO_BUF_PENDING:
+				/* No concurrent QAOB notification. */
+				break;
+			case QETH_QDIO_BUF_QAOB_OK:
+				qeth_notify_skbs(queue, buffer,
+						 TX_NOTIFY_DELAYED_OK);
+				atomic_set(&buffer->state,
+					   QETH_QDIO_BUF_HANDLED_DELAYED);
+				break;
+			case QETH_QDIO_BUF_QAOB_ERROR:
+				qeth_notify_skbs(queue, buffer,
+						 TX_NOTIFY_DELAYED_GENERALERROR);
+				atomic_set(&buffer->state,
+					   QETH_QDIO_BUF_HANDLED_DELAYED);
+				break;
+			default:
+				WARN_ON_ONCE(1);
+			}
+		}
+
 		QETH_CARD_TEXT_(card, 5, "pel%u", bidx);
 
 		/* prepare the queue slot for re-use: */
-- 
2.17.1

[PATCH net 4/4] s390/qeth: fix tear down of async TX buffers

[Julian Wiedmann]

When qeth_iqd_tx_complete() detects that a TX buffer requires additional
async completion via QAOB, it might fail to replace the queue entry's
metadata (and ends up triggering recovery).

Assume now that the device gets torn down, overruling the recovery.
If the QAOB notification then arrives before the tear down has
sufficiently progressed, the buffer state is changed to
QETH_QDIO_BUF_HANDLED_DELAYED by qeth_qdio_handle_aob().

The tear down code calls qeth_drain_output_queue(), where
qeth_cleanup_handled_pending() will then attempt to replace such a
buffer _again_. If it succeeds this time, the buffer ends up dangling in
its replacement's ->next_pending list ... where it will never be freed,
since there's no further call to qeth_cleanup_handled_pending().

But the second attempt isn't actually needed, we can simply leave the
buffer on the queue and re-use it after a potential recovery has
completed. The qeth_clear_output_buffer() in qeth_drain_output_queue()
will ensure that it's in a clean state again.

Fixes: 72861ae792c2 ("qeth: recovery through asynchronous delivery")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
 drivers/s390/net/qeth_core_main.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 48f9e4a027bf..e27319de7b00 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -500,12 +500,6 @@ static void qeth_cleanup_handled_pending(struct qeth_qdio_out_q *q, int bidx,
 
 		}
 	}
-	if (forced_cleanup && (atomic_read(&(q->bufs[bidx]->state)) ==
-					QETH_QDIO_BUF_HANDLED_DELAYED)) {
-		/* for recovery situations */
-		qeth_init_qdio_out_buf(q, bidx);
-		QETH_CARD_TEXT(q->card, 2, "clprecov");
-	}
 }
 
 static void qeth_qdio_handle_aob(struct qeth_card *card,
-- 
2.17.1

Re: [PATCH net 0/4] s390/qeth: fixes 2020-11-20

[Jakub Kicinski]

On Fri, 20 Nov 2020 10:09:35 +0100 Julian Wiedmann wrote:
> please apply the following patch series to netdev's net tree.
> 
> This brings several fixes for qeth's af_iucv-specific code paths.
> 
> Also one fix by Alexandra for the recently added BR_LEARNING_SYNC
> support. We want to trust the feature indication bit, so that HW can
> mask it out if there's any issues on their end.

Applied, thank you!