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Date:      Wed, 3 May 2000 09:45:28 +0100 (BST)
From:      Doug Rabson <dfr@nlsystems.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Gary Jennejohn <garyj@muc.de>, freebsd-current@freebsd.org
Subject:   Re: NFS, rl0 and Alpha
Message-ID:  <Pine.BSF.4.21.0005030942040.47945-100000@salmon.nlsystems.com>
In-Reply-To: <200005022114.OAA57726@apollo.backplane.com>

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On Tue, 2 May 2000, Matthew Dillon wrote:

> 
> :Is anyone else observing kernel panics in the NFS code with Alpha
> :(pc164) and rl0 (the Alpha is running as a client only) ?
> :
> :NFS worked just fine when I had a de0 in the box. After installing an
> :rl0 (I know they suck, but they're so cheap :) I _always_ get an
> :unaligned access panic when I try to access an NFS mounted FS, in any
> :way.
> 
>     This is almost certainly related to differences in how the
>     packet is aligned in memory between de0 and rl0.
> 
>     If you are getting panics, it is probably at the same
>     location every time.  If you can get a kernel core dump
>     and backtrace I'll bet we can find and fix this problem
>     quickly.

Bill put workarounds for the alpha's alignment restrictions into some of
his drivers but it seems that he missed out rl. Basically the part of the
packet which includes headers needs to have the start of the ip header
aligned to a 4-byte boundary. Since the preceding ethernet header is not
padded to 4 bytes, this often means copying the first part of the packet
to another mbuf.

-- 
Doug Rabson				Mail:  dfr@nlsystems.com
Nonlinear Systems Ltd.			Phone: +44 20 8442 9037




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