[Xen-devel] Re: [PATCH] net: xen-netback: convert to hw_features

[Michał Mirosław <mirq-linux@xxxxxxxxxxxx>]

On Tue, Apr 19, 2011 at 02:17:53PM +0100, Ian Campbell wrote:
> On Tue, 2011-04-19 at 12:56 +0100, Michał Mirosław wrote:
> > Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
> Thanks for beating me to this! However the prototype for
> xenvif_fix_features is wrong (needs to take a net_device not a xenvif).

I'll resend v2 with this fix.

> I fixed it with the following, I also moved the !can_sg MTU clamping
> into a set_features hook (like we do with netfront). Am I right that
> this pattern copes with changes to SG via ethtool etc better? I think
> it's more future proof in any case.

This looks wrong. Even if SG is turned on, you might get big skbs which
are linearized. There is a difference in SG capability and SG offload
status and as I see it the capability is what you need to test for MTU.

> NB: I'm having some issues with my test hardware at the moment so this
> is reviewed by eye and compile tested only...
> 
> I'm also happy for this to be folded into the original with my
> "Signed-off-/Acked-by Ian Campbell <ian.campbell@xxxxxxxxxx>" if that is
> preferable.

Thanks.

Best Regards,
Michał Mirosław

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