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Date: Fri, 3 Oct 2008 13:56:30 -0600 (MDT)
From: Scott Long <scottl@samsco.org>
To: Jack Vogel <jfvogel@gmail.com>
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Cc: "freebsd-net@freebsd.org" <freebsd-net@FreeBSD.org>,
	Jeff Roberson <jroberson@jroberson.net>,
	Kip Macy <kmacy@FreeBSD.org>, John Baldwin <jhb@yahoo-inc.com>
Subject: Re: potential nasty bug in igb and ixgbe
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I'll bite.

Scott


On Wed, 1 Oct 2008, Jack Vogel wrote:

> Jeff Roberson uncovered an issue that might be behind any number of
> possible problems.
>
> Our newer hardware (meaning those supported by the igb and ixgbe
> drivers) overwrites the buffer address in the RX
> descriptor with a variety of data in support of advanced features (see
> the relevant header files for details).
>
> However, in the rxeof code, if you fail to get a new mbuf, and hence,
> will discard, the descriptor is being left in the wb form,
> meaning that the address is jibberish for the next time the engine
> uses that descriptor.
>
> I am modifying get_buf so that it fixes the address in the descriptor
> when this happens. I know when my test group has had
> the igb driver under heavy load they have had some panics, right now
> I'm not sure if this has been at the root of those or not.
>
> If you want to see how I'm changing the code just speak up :) And
> thanks for finding this Jeff.
>
> Jack
>