linux-kernel - Re: 2.6.31 regression: e1000e jumbo frames no longer work: 'Unsupported MTU setting'

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Message-ID: <5f2db9d90909261914l3a927f4cya1dc5e4548688bce@mail.gmail.com>
Date:	Sat, 26 Sep 2009 19:14:55 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Nix <nix@...eri.org.uk>
Cc:	e1000-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	netdev <netdev@...r.kernel.org>, bruce.w.allan@...el.com
Subject: Re: 2.6.31 regression: e1000e jumbo frames no longer work: 
	'Unsupported MTU setting'

On Sat, Sep 26, 2009 at 4:16 AM, Nix <nix@...eri.org.uk> wrote:
> [Bruce, you have changes in net-next in this area, so you might have a clue
>  what's going on here.]
>
> In 2.6.30.x, I was happily bringing up the 82574L cards in one server like
> this:
>
> ip link set fastnet up mtu 7200
>
> As of 2.6.31.x, what I see is this:
>
> spindle:/root# ip link set mtu 7200 dev fastnet
> RTNETLINK answers: Invalid argument
> [ 3380.261796] 0000:02:00.0: fastnet: Unsupported MTU setting
>
> As far as I can tell, all MTUs above 1500 now fail.
>
> 'Unsupported' or not, this used to work, and I'd certainly expect jumbo
> frames to be supported on a gigabit card!
>
> I can't see any terribly relevant changes to e1000e between 2.6.30 and
> 2.6.31, so I'm Cc:ing netdev on the offchance that this is something
> more generic (unlikely, as 7200-byte MTUs still work fine in 2.6.31 with
> the r8169 I'm typing this on, but that doesn't help if half the subnet
> is forced to use MTUs of 1500).

It looks like the problem is that the 82574 and 82583 seem to have
their max_hw_frame_size values swapped.  You might try applying the
patch below.  I am not sure if it will apply since I hand generated it
using the git patch that seems to have introduced the problem, and I
am sending the patch through an untested account that may mangle the
patch.  I will see about submitting an official patch for this
sometime next few days.

Thanks,

Alex

diff --git a/drivers/net/e1000e/82571.c b/drivers/net/e1000e/82571.c
--- a/drivers/net/e1000e/82571.c
+++ b/drivers/net/e1000e/82571.c
@@ -1803,7 +1803,7 @@ struct e1000_info e1000_82574_info = {
 				  | FLAG_HAS_AMT
 				  | FLAG_HAS_CTRLEXT_ON_LOAD,
 	.pba			= 20,
-	.max_hw_frame_size	= ETH_FRAME_LEN + ETH_FCS_LEN,
+	.max_hw_frame_size	= DEFAULT_JUMBO,
 	.get_variants		= e1000_get_variants_82571,
 	.mac_ops		= &e82571_mac_ops,
 	.phy_ops		= &e82_phy_ops_bm,
@@ -1820,7 +1820,7 @@ struct e1000_info e1000_82583_info = {
 				  | FLAG_HAS_AMT
 				  | FLAG_HAS_CTRLEXT_ON_LOAD,
 	.pba			= 20,
-	.max_hw_frame_size	= DEFAULT_JUMBO,
+	.max_hw_frame_size	= ETH_FRAME_LEN + ETH_FCS_LEN,
 	.get_variants		= e1000_get_variants_82571,
 	.mac_ops		= &e82571_mac_ops,
 	.phy_ops		= &e82_phy_ops_bm,
--
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