linux-kernel - [PATCH 4.16 075/279] s390/qeth: use Read device to query hypervisor for MAC

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Message-Id: <20180618080611.924891226@linuxfoundation.org>
Date:   Mon, 18 Jun 2018 10:11:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Julian Wiedmann <jwi@...ux.vnet.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.16 075/279] s390/qeth: use Read device to query hypervisor for MAC

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Julian Wiedmann <jwi@...ux.vnet.ibm.com>

[ Upstream commit b7493e91c11a757cf0f8ab26989642ee4bb2c642 ]

For z/VM NICs, qeth needs to consider which of the three CCW devices in
an MPC group it uses for requesting a managed MAC address.

On the Base device, the hypervisor returns a default MAC which is
pre-assigned when creating the NIC (this MAC is also returned by the
READ MAC primitive). Querying any other device results in the allocation
of an additional MAC address.

For consistency with READ MAC and to avoid using up more addresses than
necessary, it is preferable to use the NIC's default MAC. So switch the
the diag26c over to using a NIC's Read device, which should always be
identical to the Base device.

Fixes: ec61bd2fd2a2 ("s390/qeth: use diag26c to get MAC address on L2")
Signed-off-by: Julian Wiedmann <jwi@...ux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/s390/net/qeth_core_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -4839,7 +4839,7 @@ int qeth_vm_request_mac(struct qeth_card
 		goto out;
 	}

-	ccw_device_get_id(CARD_DDEV(card), &id);
+	ccw_device_get_id(CARD_RDEV(card), &id);
 	request->resp_buf_len = sizeof(*response);
 	request->resp_version = DIAG26C_VERSION2;
 	request->op_code = DIAG26C_GET_MAC;