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From: ebiederm@xmission.com (Eric W. Biederman)
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Date: Wed, 15 May 2013 09:53:06 -0700
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 (Dave Lloyd's message of "Wed, 15 May 2013 10:50:40 -0500")
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Subject: Re: Kernel panics when using kexec for rebooting
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To: Dave Lloyd <dave@davelloyd.com>
Cc: kexec@lists.infradead.org

Dave Lloyd <dave@davelloyd.com> writes:

> On Tue, May 14, 2013 at 6:14 PM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>
>>
>> Oh. Yeah.  IB definitely sets up memory for ongoing dma.  So if it
>> doesn't have a shutdown method and IB traffic comes in during boot just
>> about anything cood happen.
>>
>>> I'm inclined to chalk the ACPI Error mesages up to potentially buggy
>>> BIOS/hardware from the vendor since pata_amd and pata_acpi are in wide
>>> use and I would expect to see more issues reported were there truly an
>>> issue with rebooting with kexec and not unloading pata_amd and
>>> pata_acpi.
>>
>> Maybe.  Or it might be luck of timing, which memory was stomped when
>> incomming IB packets stomped on memory.
>>
>> Eric
>>
>
> Removing the infiniband drivers in /etc/init.d/halt right before the
> kexec -e definitely seems to have done the trick. Thanks!
>
> My follow up question is, if we are clearing the bus master DMA bit,
> why are the Mellanox not reset or at least stop doing DMA until the
> driver is loaded again? Is this a case of the Mellanox hardware
> needing an extra poke to do the right thing?

Some hardware does not respect the bus master bit.  I assume that Mellanox
has that problem.

Eric

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