linux-kernel - Re: [PATCH v5] irq: add quirk for broken interrupt remapping on 55XX chipsets

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Message-ID: <20130405192949.GA1094@hmsreliant.think-freely.org>
Date:	Fri, 5 Apr 2013 15:29:49 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	linux-kernel@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>,
	Don Zickus <dzickus@...hat.com>,
	Don Dutile <ddutile@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Asit Mallick <asit.k.mallick@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH v5] irq: add quirk for broken interrupt remapping on 55XX
 chipsets

On Fri, Apr 05, 2013 at 03:25:54PM -0400, Neil Horman wrote:
> A few years back intel published a spec update:
> http://www.intel.com/content/dam/doc/specification-update/5520-and-5500-chipset-ioh-specification-update.pdf
> 
> For the 5520 and 5500 chipsets which contained an errata (specificially errata
> 53), which noted that these chipsets can't properly do interrupt remapping, and
> as a result the recommend that interrupt remapping be disabled in bios.  While
> many vendors have a bios update to do exactly that, not all do, and of course
> not all users update their bios to a level that corrects the problem.  As a
> result, occasionally interrupts can arrive at a cpu even after affinity for that
> interrupt has be moved, leading to lost or spurrious interrupts (usually
> characterized by the message:
> kernel: do_IRQ: 7.71 No irq handler for vector (irq -1)
> 
> There have been several incidents recently of people seeing this error, and
> investigation has shown that they have system for which their BIOS level is such
> that this feature was not properly turned off.  As such, it would be good to
> give them a reminder that their systems are vulnurable to this problem.
> 
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Prarit Bhargava <prarit@...hat.com>
> CC: Don Zickus <dzickus@...hat.com>
> CC: Don Dutile <ddutile@...hat.com>
> CC: Bjorn Helgaas <bhelgaas@...gle.com>
> CC: Asit Mallick <asit.k.mallick@...el.com>
> CC: David Woodhouse <dwmw2@...radead.org>
> CC: linux-pci@...r.kernel.org
> ---
> 
> Change notes:
> 
> v2)
> 
> * Moved the quirk to the x86 arch, since consensus seems to be that the 55XX
> chipset series is x86 only.  I decided however to keep the quirk as a regular
> quirk, not an early_quirk.  Early quirks have no way currently to determine if
> BIOS has properly disabled the feature in the iommu, at least not without
> significant hacking, and since its quite possible this will be a short lived
> quirk, should Don Z's workaround code prove successful (and it looks like it may
> well), I don't think that necessecary.
> 
> * Removed the WARNING banner from the quirk, and added the HW_ERR token to the
> string, I opted to leave the newlines in place however, as I really couldnt
> find a way to keep the text on a single line is still legible from a code
> perspective.  I think theres enough language in there that using cscope on just
> about any substring however will turn it up, and again, this may be a short
> lived quirk.
> 
> v3)
> 
> * Removed defines from pci_ids.h, and used direct id values as per request from
> Bjorn.
> 
> v4)
> 
> * Converted pr_warn to WARN_TAINT(TAINT_FIRMWARE_WORKAROUND) as per David
> Woodhouse
> 
> v5)
> 
> * Moved check to an early quirk, and flagged the broken chip, so we could
> reasonably disable irq remapping during bootup.


Self NAK, sorry, I've got extra water in the quirks file left over from my move.

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