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

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Date:	Sun, 16 Mar 2014 12:55:47 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	lkml <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: Info: mapping multiple BARs. Your kernel is fine.

On Sat, Mar 15, 2014 at 03:15:04PM +0100, Rafael J. Wysocki wrote:
> I've just gone throught this.

Thanks.

> So the problem is that we have the PNP "system" driver whose only purpose seems
> to be to reserve system resources so that the PCI layer doesn't assign them to
> new devices on hotplug (disclaimer: I didn't invent it, I only read the code and
> comments in there).
> 
> It does that for ACPI device objects having the "PNP0C02" and "PNP0C01" IDs.

Right, pnp 00:01 is PNP0C02.

> Apparently, snb_uncore_imc_init_box() steps on a range already reserved by that
> driver on your box.  And this doesn't seem to be a coincidence, because the ACPI
> device object in question probably *does* correspond to the memory controller
> that the uncore driver attempts to use.
> 
> I'm not sure how to address that right now to be honest.  Arguably, the PNP
> "system" driver should be replaced with something saner, but still the
> resources it claims need to be kept out of reach of the PCI's resource
> allocation code.

Well, I'm only conjecturing here but there should be a way for the
uncore code to tell the PNP "system" driver to free this resource
because uncore is going to use it now. Or something to that effect.

Oh well.
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