linux-kernel - Re: [PATCH 4/5] x86: acpi: Print warning for malformed host bridge resources

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Message-ID: <1355489504.2588.0.camel@thor>
Date:	Fri, 14 Dec 2012 07:51:44 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 4/5] x86: acpi: Print warning for malformed host bridge
 resources

Ping?

On Sun, 2012-11-11 at 09:49 -0500, Peter Hurley wrote:
> On Sat, 2012-11-10 at 14:52 -0700, Bjorn Helgaas wrote:
> > On Wed, Nov 7, 2012 at 7:55 PM, Peter Hurley <peter@...leysoftware.com> wrote:
> > > An incorrectly specified host bridge window may prevent
> > > other devices from claiming assigned resources. For example,
> > > this flawed _CRS resource descriptor from a Dell T5400:
> > >      DWordMemory (ResourceProducer, PosDecode, MinFixed, MaxFixed, NonCacheable, ReadWrite,
> > >          0x00000000,         // Granularity
> > >          0xF0000000,         // Range Minimum
> > >          0xFE000000,         // Range Maximum
> > >          0x00000000,         // Translation Offset
> > >          0x0E000000,         // Length
> > >          ,, , AddressRangeMemory, TypeStatic)
> > 
> > I think the problem here is that the Range Maximum should be
> > 0xFDFFFFFF, not 0xFE000000, right?
> 
> I presume so.
> 
> > > diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> > > index 192397c..3468d16 100644
> > > --- a/arch/x86/pci/acpi.c
> > > +++ b/arch/x86/pci/acpi.c
> > > @@ -298,6 +298,10 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > >                         "host bridge window [%#llx-%#llx] "
> > >                         "([%#llx-%#llx] ignored, not CPU addressable)\n",
> > >                         start, orig_end, end + 1, orig_end);
> > > +       } else if (flags & IORESOURCE_MEM && (start & 0x0f || ~end & 0x0f)) {
> > > +               dev_warn(&info->bridge->dev,
> > > +                        "invalid host bridge window [%#llx-%#llx]\n",
> > > +                        start, end);
> > 
> > We didn't actually *fix* anything here, so I guess we're just pointing
> > out the reason for a subsequent failure to claim the adjacent
> > resource.
> 
> Correct. There is no fix; only a diagnostic warning.
> 
> The warning is also a 'red flag' that, on this machine, it might be
> better to boot the kernel with the "pci=nocrs" option.
> 
> > As far as I know, the spec doesn't actually require resources of ACPI
> > devices to be non-overlapping.  Windows accepts overlapping resources,
> > and I think Linux probably should, too, but right now we trip over
> > this.
> 
> (note: I included a link below to the defect report which has
> the /proc/iomem, dmesg & dmidecode)
> 
> The situation is this:
> 
> The adjacent resources (northbridge & southbridge) are not defined by
> ACPI, but rather reserved with an e820 address descriptor from
> [0xfe000000-0xfeffffff], so strictly speaking there is no overlapping
> ACPI resource.
> 
> The e820 descriptor is bumped out to [0xf0000000-0xfeffffff] and the
> malformed host bridge window is reparented to it.
> 
> At this point in the boot, there is no resource conflict.
> 
> Later in the boot, the i5k_amb driver tries to map
> [0xfe000000-0xfe01ffff] which is the FB-DIMM AMB register window on the
> Intel 5400 MCH and is rejected. The request is rejected because the
> requested range does not map completely to a single parent and this is
> not allowed. (The i5k_amb driver exposes the FB-DIMM temperature sensors
> through sysfs).
> 
> There is no problem in Windows because no driver attempts to allocate
> [0xfe000000-0xfe01ffff]. However, I doubt the PNP Manager would allow
> another bus pdo to claim an overlapping resource with PCI bus 0. I
> suspect the offending device would yellow bang. (That would be an
> interesting experiment...)
> 
> > In the meantime (until we figure out how to handle overlapping
> > resources better), can we do something to actually fix this?  Maybe we
> > should truncate the end of the range to 0xFDFFFFFF like we do for
> > non-addressable parts of the range?
> 
> Auto-fixing this seems problematic because it's essentially impossible
> to determine if the resource length or the resource end or both is
> wrong.
> 
> > Is there a bugzilla or a complete dmesg log to look at?
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=50161
> 
> Regards,
> Peter Hurley
> 
> 


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