linux-kernel - Re: Info: mapping multiple BARs. Your kernel is fine.

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Date:	Wed, 16 Apr 2014 17:11:28 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"Lu, Aaron" <aaron.lu@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Yan, Zheng Z" <zheng.z.yan@...el.com>
Subject: Re: Info: mapping multiple BARs. Your kernel is fine.

On Wed, Apr 16, 2014 at 5:08 PM, Stephane Eranian <eranian@...gle.com> wrote:
> On Wed, Apr 16, 2014 at 1:31 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>> On Wed, Apr 16, 2014 at 09:04:04PM +0200, Borislav Petkov wrote:
>>> On Thu, Mar 20, 2014 at 02:48:30PM -0600, Bjorn Helgaas wrote:
>>> > Right.  Even if we had this long-term solution, we'd still have
>>> > Stephane's current problem, because the PNP0C02 _CRS is still wrong.
>>> >
>>> > We do have a drivers/pnp/quirks.c where we could conceivably adjust
>>> > the PNP resource if we found the matching PCI device and MCHBAR.  That
>>> > should solve Stephane's problem even with the current
>>> > drivers/pnp/system.c.
>>>
>>> Guys, this still triggers in -rc1. Do we have a fix or something
>>> testable at least?
>>
>> Hi Boris,
>>
>> Can you try the patch below?
>>
>>
>>
>> PNP: Work around Haswell BIOS defect in MCH area reporting
>>
>> From: Bjorn Helgaas <bhelgaas@...gle.com>
>>
>> Work around a Haswell BIOS defect that causes part of the MCH area to be
>> unreported.
>>
>> MCHBAR is not an architected PCI BAR, so MCH space is usually reported as a
>> PNP0C02 resource.  The MCH space was 16KB prior to Haswell, but it is 32KB
>> in Haswell.  Some Haswell BIOSes still report a PNP0C02 resource that is
>> only 16KB, which means the rest of the MCH space is consumed but
>> unreported.
>>
> Why are you saying this is Haswell vs. others. I see the problem on my
> IvyBridge laptop, like Boris.

Ah, good question.  Somewhere I got pointed to the Haswell docs, which
say 32KB.  I don't know what other parts have 32KB MCH spaces.  If we
could figure out a list of device IDs with 32KB spaces, we could add
that to the quirk.

But I don't know how to come up with a complete list.

Bjorn
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