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Date: Sun, 16 Mar 2014 12:55:47 +0100
From: Borislav Petkov <bp@alien8.de>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: lkml <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Bjorn Helgaas <bhelgaas@google.com>,
        Linux PCI <linux-pci@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Zhang Rui <rui.zhang@intel.com>, Yinghai Lu <yinghai@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Stephane Eranian <eranian@google.com>
Subject: Re: Info: mapping multiple BARs. Your kernel is fine.
Message-ID: <20140316115546.GA11935@nazgul.tnic>
References: <20140224162400.GE16457@pd.tnic>
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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.