Re: WARNING: CPU: 2 PID: 1 at arch/x86/mm/ioremap.c:171 __ioremap_caller+0x290/0x2fa()

From: Yinghai Lu
Date: Tue Jul 15 2014 - 19:40:21 EST

On Tue, Jul 15, 2014 at 1:33 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
> [+cc Yinghai, Rafael]

>> I opened this bugzilla:
>> and attached your
>> dmesg to it. I see what the problem is, but I don't have a good idea
>> yet for how to fix it.
>> The problem is that we don't handle e820 and PNP device resource
>> information correctly. From the attached dmesg, we have this:
>> BIOS-e820: [mem 0x00000000fed10000-0x00000000fed13fff] reserved
>> system 00:00: [mem 0xfed10000-0xfed17fff] could not be reserved
>> The 00:00 PNP device describes the correct 32K range for the Intel MCH
>> (see [1] for details). But the [mem 0xfed10000-0xfed13fff] entry from
>> e820 was added to the resource map first, and it covers only the first
>> 16K of the MCH range. This caused the subsequent PNP reservation to
>> fail. Then the snb_uncore_imc_init_box() reservation caused the
>> warning, because it would be a child of the e820 entry but it covers
>> more space.
>> [1] fixed a similar issue where the PNP device described only the
>> first 16K of the MCH range. This case is slightly different because
>> here it's the e820 entry that is incorrect.
>> [1]
> One of the reasons for iomem_resource is so we don't hand out the same
> address space to two different devices. We *could* do that by keeping
> track of the union of all devices and reserved areas that we know
> about.
> But the current resource code is more strict: it enforces a hierarchy.
> For example, in this case, it rejects the 00:00 PNP resource because
> it is larger than the e820 entry. The problem with rejecting it is
> that we might hand out [mem 0xfed14000-0xfed17fff] to another device
> even though PNP told us that it's in use.
> I'm about to head out for a few weeks of vacation, so I won't be able
> to do anything with this.

In that case, we could reserve the whole MCH range in e820 from
trim_snb_memory() instead.

HPA, what is your idea about it?

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