From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36531) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c8gmw-0002Od-Ux for qemu-devel@nongnu.org; Mon, 21 Nov 2016 00:05:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c8gmr-0004NY-Pv for qemu-devel@nongnu.org; Mon, 21 Nov 2016 00:05:06 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45268 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c8gmr-0004Mx-Kt for qemu-devel@nongnu.org; Mon, 21 Nov 2016 00:05:01 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uAL53ceh132863 for ; Mon, 21 Nov 2016 00:05:00 -0500 Received: from e23smtp01.au.ibm.com (e23smtp01.au.ibm.com [202.81.31.143]) by mx0b-001b2d01.pphosted.com with ESMTP id 26us0xtxap-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 21 Nov 2016 00:05:00 -0500 Received: from localhost by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 21 Nov 2016 15:04:56 +1000 From: Sam Bobroff Date: Mon, 21 Nov 2016 16:04:53 +1100 Message-Id: Subject: [Qemu-devel] [PATCH v2 1/1] hw/net/spapr_llan: 6 byte mac address device tree entry List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-ppc@nongnu.org, thuth@redhat.com The spapr-vlan device in QEMU has always presented it's MAC address in the device tree as an 8 byte value, even though PAPR requires it to be 6 bytes. This is because, at the time, AIX required the value to be 8 bytes. However, modern versions of AIX support the (correct) 6 byte value so they no longer require the workaround. It would be neatest to always provide a 6 byte value but that would cause a problem with old Linux kernel ibmveth drivers, so the old 8 byte value is still presented when necessary. Since commit 13f85203e (3.10, May 2013) the driver has been able to handle 6 or 8 byte addresses so versions after that don't need to be considered specially. Drivers from kernels before that can also handle either type of address, but not always: * If the first byte's lowest bits are 10, the address must be 6 bytes. * Otherwise, the address must be 8 bytes. (The two bits in question are significant in a MAC address: they indicate a locally-administered unicast address.) So to maintain compatibility the old 8 byte value is presented when the lowest two bits of the first byte are not 10. Signed-off-by: Sam Bobroff --- v2: Re-introduced the old workaround so that old Linux kernel drivers aren't broken, at the cost of AIX seeing the old value for for non-locally generated or broadcast addresses (this shouldn't matter because those addresses probably aren't used on virtual adapters). Reworded first paragraph of commit message because AIX seems to still support the old 8 byte value. hw/net/spapr_llan.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/hw/net/spapr_llan.c b/hw/net/spapr_llan.c index 01ecb02..b73be87 100644 --- a/hw/net/spapr_llan.c +++ b/hw/net/spapr_llan.c @@ -385,18 +385,24 @@ static int spapr_vlan_devnode(VIOsPAPRDevice *dev, void *fdt, int node_off) int ret; /* Some old phyp versions give the mac address in an 8-byte - * property. The kernel driver has an insane workaround for this; + * property. The 3.10 kernel driver has an insane workaround; * rather than doing the obvious thing and checking the property * length, it checks whether the first byte has 0b10 in the low * bits. If a correct 6-byte property has a different first byte * the kernel will get the wrong mac address, overrunning its * buffer in the process (read only, thank goodness). * - * Here we workaround the kernel workaround by always supplying an - * 8-byte property, with the mac address in the last six bytes */ - memcpy(&padded_mac[2], &vdev->nicconf.macaddr, ETH_ALEN); - ret = fdt_setprop(fdt, node_off, "local-mac-address", - padded_mac, sizeof(padded_mac)); + * Here we return a 6-byte address unless that would break a 3.10 driver. + * In that case we return a padded 8-byte address to allow the old + * workaround to succeed. */ + if ((vdev->nicconf.macaddr.a[0] & 0x3) == 0x2) { + ret = fdt_setprop(fdt, node_off, "local-mac-address", + &vdev->nicconf.macaddr, ETH_ALEN); + } else { + memcpy(&padded_mac[2], &vdev->nicconf.macaddr, ETH_ALEN); + ret = fdt_setprop(fdt, node_off, "local-mac-address", + padded_mac, sizeof(padded_mac)); + } if (ret < 0) { return ret; } -- 2.10.0.297.gf6727b0