linux-kernel - Re: kexec reboot broken with ioatdma?

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Message-ID: <20091216224912.GC16219@verge.net.au>
Date:	Thu, 17 Dec 2009 09:49:12 +1100
From:	Simon Horman <horms@...ge.net.au>
To:	Roland Dreier <rdreier@...co.com>
Cc:	linux-kernel@...r.kernel.org,
	Dan Williams <dan.j.williams@...el.com>,
	kexec@...ts.infradead.org
Subject: Re: kexec reboot broken with ioatdma?

On Wed, Dec 16, 2009 at 01:32:11PM -0800, Roland Dreier wrote:
> I have a system with IOAT hardware, and rebooting with kexec fails with
> the latest 2.6.32-git kernel.  I haven't really tried earlier kernels,
> but I suspect the issue comes from the ioatdma driver being autoloaded now.
> 
> The reboot gets stuck at:
> 
>   ioatdma 0000:00:16.0: Self-test copy timed out, disabling
>   ioatdma 0000:00:16.0: Freeing 2 in use descriptors!
>   ioatdma 0000:00:16.0: Intel(R) I/OAT DMA Engine init failed
> 
> so presumably the IOAT hardware is left in a bad state that the ioatdma
> driver in the kexec'ed new kernel can't handle.
> 
> I notice that long ago, there was a commit 428ed602 ("I/OAT: fix I/OAT
> for kexec") that added a shutdown method to clean things up so kexec
> worked, and then more recently there was 4fac7fa5 ("ioat: do not perform
> removal actions at shutdown") that got rid of the shutdown hook.
> 
> I'm not sure what the correct fix is here: fix the shutdown order so
> everyone drops all references to IOAT stuff before IOAT is shutdown, or
> add some code to the ioatdma driver so it resets the hardware on startup
> so the new kernel can deal with an unspecified state.

Hi Roland,

from a kexec point of view I believe that the preferred option is the
former - shutdown the device so it can be initialised using standard paths
in the second kernel.

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