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

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Date:	Thu, 17 Apr 2014 14:10:54 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Dave Jones <davej@...hat.com>,
	"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>,
	Stephane Eranian <eranian@...gle.com>,
	"Yan, Zheng Z" <zheng.z.yan@...el.com>
Subject: Re: Info: mapping multiple BARs. Your kernel is fine.

On Thu, Apr 17, 2014 at 1:48 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Thu, Apr 17, 2014 at 12:26:37PM -0600, Bjorn Helgaas wrote:
>> Thanks a lot for testing this out and debugging my issues.
>>
>> Here's a new version that looks for both device IDs I know about.
>>
>> I'm still nervous about the modeset problem Dave is seeing.  Since the
>> original patch wouldn't find an 8086:0c00 device on Dave's system, it
>> should have done nothing.  But since it caused a modesetting problem,
>> there's something else doing on that I don't understand.
>
> Yeah, this is strange, to put it mildly. This quirk wouldnt've done
> anything besides the iteration over the pci devices with pci_get_device.
> Which wouldn't do anything (refcount increment or so) if it didn't find
> the device, right?

Right.

> Bah, today is the day of the strange bugs. :-\
>
>> PNP: Work around BIOS defects in Intel MCH area reporting
>>
>> From: Bjorn Helgaas <bhelgaas@...gle.com>
>>
>> Work around BIOSes that don't report the entire Intel MCH area.
>>
>> MCHBAR is not an architected PCI BAR, so MCH space is usually reported as a
>> PNP0C02 resource.  The MCH space was once 16KB, but is 32KB in newer parts.
>> Some BIOSes still report a PNP0C02 resource that is only 16KB, which means
>> the rest of the MCH space is consumed but unreported.
>>
>> This can cause resource map sanity check warnings or (theoretically) a
>> device conflict if we assigned the unreported space to another device.
>>
>> The Intel perf event uncore driver tripped over this when it claimed the
>> MCH region:
>>
>>   resource map sanity check conflict: 0xfed10000 0xfed15fff 0xfed10000 0xfed13fff pnp 00:01
>>   Info: mapping multiple BARs. Your kernel is fine.
>>
>> To prevent this, if we find a PNP0C02 resource that covers part of the MCH
>> space, extend it to cover the entire space.
>>
>> Link: http://lkml.kernel.org/r/20140224162400.GE16457@pd.tnic
>> Reported-by: Borislav Petkov <bp@...en8.de>
>
> Yep, this one works fine:
>
> [    0.403855] pnp 00:01: [Firmware Bug]: PNP resource [mem 0xfed10000-0xfed13fff] covers only part of 0000:00:00.0 Intel MCH; extending to [mem 0xfed10000-0xfed17fff]
>
> Acked-by: Borislav Petkov <bp@...e.de>
> Tested-by: Borislav Petkov <bp@...e.de>

>> +     region.end = region.start + 32*1024 - 1 ;

> checkpatch complains about a trailing space before the semicolon.

Thanks!  I hate typos like that.

I'll fix this, add your tested-by and ack, and send to Rafael.

Bjorn
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