linux-kernel - Re: BUG in drivers/dma/ioat/dma

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Date:	Wed, 30 Jun 2010 23:51:51 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	"Woodhouse, David" <david.woodhouse@...el.com>
CC:	Chris Li <lkml@...isli.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: BUG in drivers/dma/ioat/dma_v2.c:314

On 6/30/2010 11:21 PM, Woodhouse, David wrote:
> On Wed, 2010-06-30 at 22:44 +0100, Williams, Dan J wrote:
>> I don't see a way around this beyond blacklisting this (platform, vt-d
>> setting, driver) combination.  Is there a quirk infrastructure for this
>> sort of problem?
>
> Yeah, kind of. If the IOAT PCI device _always_ has its own IOMMU, we
> could have a quirk for it which says it must _never_ be matched by a
> catch-all IOMMU. That would probably solve it?
>

This version of the device only exists on the 5400 chipset and always 
has its own iommu, but since other platforms get the DMAR entry right I 
think this hammer is too big?  Wouldn't this break VT-d operation on 
non-busted platforms?

Alternatively I can just catch this failure earlier in the init process 
and fail the driver load with a grumble printk about broken bios... 
instead of the current BUG_ON() that is meant to catch runtime catastrophes.

--
Dan
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