From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45675) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cdTpB-0003Qi-LI for qemu-devel@nongnu.org; Mon, 13 Feb 2017 22:30:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cdTp8-0004Lb-Bh for qemu-devel@nongnu.org; Mon, 13 Feb 2017 22:30:41 -0500 Date: Tue, 14 Feb 2017 14:23:48 +1100 From: David Gibson Message-ID: <20170214032348.GE2169@umbus.fritz.box> References: <4c44ad5045020be90edfdc8787002e09691db1d3.1479770377.git.sam.bobroff@au1.ibm.com> <20170213053340.GC25381@umbus> <602f2661-0d45-d135-e3f8-64426329a736@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="/2994txjAzEdQwm5" Content-Disposition: inline In-Reply-To: <602f2661-0d45-d135-e3f8-64426329a736@redhat.com> Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH v3 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: Thomas Huth Cc: Sam Bobroff , qemu-devel@nongnu.org, qemu-ppc@nongnu.org --/2994txjAzEdQwm5 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 13, 2017 at 08:36:45AM +0100, Thomas Huth wrote: > On 13.02.2017 06:33, David Gibson wrote: > > On Tue, Nov 22, 2016 at 10:19:38AM +1100, Sam Bobroff wrote: > >> 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 > >=20 > > Sorry, I didn't see this one until now. > >=20 > > Since we need a workaround for the workaround, is it actually worth > > going to the 6-byte property? >=20 > 8-byte addresses are just wrong, all other network devices and the > standard use 6-byte MAC addresses instead. So we should use 6-byte > addresses in QEMU whenever it is possible, too. Unfortunately there are > still guests in the field that use this bad assumption with 8 byte > addresses, so I think this work-around is the best we can and should do > right now. Hm, yes, good point. Applied to ppc-for-2.9. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --/2994txjAzEdQwm5 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJYonhCAAoJEGw4ysog2bOS2F4QAJTePCsmPjWybnds9fLSxi90 7qdwzpUBclu9UxOMF3K6AVN0lmOaws6+wiUGhdeYRXH2yXkXIReenZYF4HFuQseL XmF9P1emHbmxh8oECyZ3+AraFyQGvjxzEwnm8SPXH+wIEvO93h/aWoAZosEYvvq5 LyAGcPCGTklGfSxMLAQz4OdvR/o8PlQJnJ423MWWRluFt8XZkGRh4poKKd32WZuX fpxLCmEK7XD642v8IU4P19nU7hQrG332Ehet/zrzJDirBjgCRN8pcQpq7Aa6XVNm Yx1PRrS/xwXbTT7PM8VruizYATt7BkRve5TS9g5cjbZrKd7TreN1n8coBDpRvUA+ sHjmWjThSPibXn218nZWCXhLya+ChjGTzoILKusyhNzVglAG4MxlvPPUG15PPuYW xg9kK06q5E34mNRphoUO18lBTzy0mPdKZUlBRe52NjuaSFXir5FEreUI3WxwxKJP H26EaDGGDvTHQmAlBZDTjtaKcRpeOvyDrxcnh6GHLTNIV5kqSNhm6rfWe+VYKITZ mZfhqXwve/ev6F1w3w8jtbWSYaXeTJqKJZdEoBBw15RWjABGzEdvf9LrvtTqfAX5 zF6+SYmvnFJftFzZVlabMAmsyxfD/FGKTW5zApGLVbe9CjGZiaCTmiO3bkkcG1LR 3dgTBNyc75eBe5NjKCYM =s2kC -----END PGP SIGNATURE----- --/2994txjAzEdQwm5--