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

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Date:	Thu, 17 Dec 2009 10:36:13 +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 03:04:03PM -0800, Roland Dreier wrote:
> 
>  > 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.
> 
> OK... however I'm not suggesting a separate kexec initialization path,
> simply adding a reset of the device in the standard initialization.
> This would be fairly normal for other types of device; for example, the
> BIOS may have left a NIC in an undefined state due to network boot.  Of
> course BIOS is unlikely to use an IOAT DMA engine but the principle of
> limiting assumptions about platform state still stands I think.

If its reset in a standard path, then yes that seems sensible to me.
I'm mainly concerned about avoiding something along the lines of:

	if (is_booting_from_kexec)
		reset_hw();

> >From a quick look, it seems tricky to get a clean shutdown of IOAT stuff
> since there doesn't seem to be a clean ordering that makes sure the
> ioatdma stuff is shutdown after everything using it.
> 
>  - R.
> 
> 
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