Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V

From: Vitaly Kuznetsov
Date: Thu Sep 17 2015 - 05:03:37 EST


David Miller <davem@xxxxxxxxxxxxx> writes:

> From: David Laight <David.Laight@xxxxxxxxxx>
> Date: Wed, 16 Sep 2015 16:25:03 +0000
>
>> Am I right in thinking this is adding an extra 96 unused bytes to the front
>> of almost all skb just so that hyper-v can make its link level header
>> contiguous with whatever follows (IP header ?).
>>
>> Doesn't sound ideal.
>
> Agreed, this is rediculous, and the entire stack will incur this cost
> just because hyperv is enabled in the kernel config.

That's what 'RFC' in the subject was about :-)

We already have a precedent of increasing LL_MAX_HEADER globaly because
of a config option (CONFIG_MAC80211_MESH) but Hyper-V needs more.

--
Vitaly
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