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

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Date:	Thu, 01 Jul 2010 00:26:17 -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 7/1/2010 12:12 AM, Woodhouse, David wrote:
> On Thu, 2010-07-01 at 07:51 +0100, Williams, Dan J wrote:
>> 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?
>
> That just means we have to get the quirk right. Does 'this version' of
> the device have its own PCI ID? We can always fall back to checking the
> ID of the device at 0000:00:00.0 to check which chipset we're on.
>

PCI_DEVICE_ID_INTEL_IOAT_SNB only exists on this chipset and to date 
only "MacPro3,1" platforms have this problem.

>> 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.
>
> Please use WARN_TAINT(TAINT_FIRMWARE_WORKAROUND). That way the
> statistics end up in kerneloops.org and we have found that extremely
> useful when LARTing the offending vendors.
>

Good to know, thanks.

--
Dan
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