From: Julian Wiedmann <jwi@linux.ibm.com>
Subject: s390/qeth: improve fallback to random MAC address
Patch-mainline: v4.18-rc1
Git-commit: 21b1702af12eb62bb40d994c9c1546ecacfc8456
References: FATE#326350, LTC#169511, bsc#1113509

Summary:     qeth: performance improvements
Description: This adds recent functional and performance improvements for the
             qeth network driver.
             Primarily this brings Scatter-Gather support for HiperSockets,
             reduced CPU consumption in the L3 IPv4 transmit path for OSA,
             improved Promiscuous Mode performance due to IFF_UNICAST_FLT,
             support for Scatter-Gather on z/VM virtual NICs, and
             support for delayed GRO flushing.

             For sanity & stability reasons, this effectively constitutes a
             backport of the qeth device driver from 4.19 mainline.
             

Upstream-Description:

             s390/qeth: improve fallback to random MAC address

             If READ MAC fails to fetch a valid MAC address, allow some more device
             types (IQD and z/VM OSD) to fall back to a random address.
             Also use eth_hw_addr_random(), for indicating to userspace that the
             address type is NET_ADDR_RANDOM.

             Note that while z/VM has various protection schemes to prohibit
             custom addresses on its NICs, they are all optional. So we should at
             least give it a try.

             Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
             Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/s390/net/qeth_l2_main.c |   23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -439,7 +439,6 @@ static int qeth_l2_process_inbound_buffe
 static int qeth_l2_request_initial_mac(struct qeth_card *card)
 {
 	int rc = 0;
-	char vendor_pre[] = {0x02, 0x00, 0x00};
 
 	QETH_DBF_TEXT(SETUP, 2, "l2reqmac");
 	QETH_DBF_TEXT_(SETUP, 2, "doL2%s", CARD_BUS_ID(card));
@@ -459,16 +458,20 @@ static int qeth_l2_request_initial_mac(s
 	    card->info.type == QETH_CARD_TYPE_OSX ||
 	    card->info.guestlan) {
 		rc = qeth_setadpparms_change_macaddr(card);
-		if (rc) {
-			QETH_DBF_MESSAGE(2, "couldn't get MAC address on "
-				"device %s: x%x\n", CARD_BUS_ID(card), rc);
-			QETH_DBF_TEXT_(SETUP, 2, "1err%04x", rc);
-			return rc;
-		}
-	} else {
-		eth_random_addr(card->dev->dev_addr);
-		memcpy(card->dev->dev_addr, vendor_pre, 3);
+		if (!rc)
+			goto out;
+		QETH_DBF_MESSAGE(2, "READ_MAC Assist failed on device %s: x%x\n",
+				 CARD_BUS_ID(card), rc);
+		QETH_DBF_TEXT_(SETUP, 2, "1err%04x", rc);
+		/* fall back once more: */
 	}
+
+	/* some devices don't support a custom MAC address: */
+	if (card->info.type == QETH_CARD_TYPE_OSM ||
+	    card->info.type == QETH_CARD_TYPE_OSX)
+		return (rc) ? rc : -EADDRNOTAVAIL;
+	eth_hw_addr_random(card->dev);
+
 out:
 	QETH_DBF_HEX(SETUP, 2, card->dev->dev_addr, card->dev->addr_len);
 	return 0;