netdev - RE: [PATCH] mlx4_en: fix transmit of packages when blue frame is enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 10 Oct 2011 10:29:40 +0200
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Eli Cohen <eli@....mellanox.co.il>, netdev@...r.kernel.org,
	Eli Cohen <eli@...lanox.co.il>, linuxppc-dev@...ts.ozlabs.org,
	Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>,
	Yevgeny Petrilin <yevgenyp@...lanox.co.il>
Subject: RE: [PATCH] mlx4_en: fix transmit of packages when blue frame is
 enabled

On Mon, 2011-10-10 at 09:20 +0100, David Laight wrote:
> 
> For the above I'd actually suggest making 'doorbell_qpn' have the
> correct endianness in order to avoid the (potential) swap every
> time it is set.

Well, the problem is that either you'll end up swapping on x86 or you'll
end up swapping on ppc, there is no "native" MMIO accessor that allow
you to do a no-swap access whatever the arch you are on. Or rather,
there is the __raw_ one but you shouldn't use it for most things :-)
(Because it also doesn't have the right memory barriers).

So I'd rather they do it right using the simpler method, the cost of
swap is going to be negligible, probably not even measurable, and if and
only if they think they can improve on that in a second step, then
consider doing otherwise with appropriate measurements showing a
significant difference.

> You also need to treble-check the required endianness for the
> 'vlan_tag' in the tx descriptor. What would be needed is the
> MAC PCI slave were on an x86 (LE) system.

Cheers,
Ben.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html