linux-kernel - Re: [PATCH v4 0/5] PCI: try "pci=use

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Message-ID: <20100219005836.GA26564@us.ibm.com>
Date:	Thu, 18 Feb 2010 16:58:36 -0800
From:	Gary Hade <garyhade@...ibm.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Tony Luck <tony.luck@...el.com>, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, Peter Haight <peterh@...ros.com>,
	Gary Hade <garyhade@...ibm.com>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, linux-am33-list@...hat.com,
	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Larry Finger <Larry.Finger@...inger.net>
Subject: Re: [PATCH v4 0/5] PCI: try "pci=use_crs" again

On Wed, Feb 17, 2010 at 01:19:47PM -0700, Bjorn Helgaas wrote:
> Historically, Linux has assumed a single PCI host bridge, with that bridge
> claiming all the address space left after RAM and legacy devices are taken out.
> 
> If the system contains multiple host bridges, we can no longer operate under
> that assumption.  We have to know what parts of the address space are claimed
> by each bridge so that when we assign resources to a PCI device, we take them
> from a range claimed by the upstream host bridge.
> 
> On x86 and ia64, we use ACPI to enumerate all the PCI host bridges in the
> system, and part of the host bridge description is the "_CRS" (current resource
> settings" property, which lists the address space used by the bridge.  On x86,
> we currently ignore most of the _CRS information.  This patch series changes
> this, so we will use _CRS to learn about the host bridge windows.
> 
> Since most x86 machines with multiple host bridges are relatively new, this
> series only turns this on for machines with BIOS dates of 2008 or newer.

I just tried your changes on an IBM x3850 with a 12/01/2008 BIOS
date.  After booting without pci=use_crs I observed the expected
  PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug
message.  I then loaded 'acpiphp' and was able to successfully 
hot-remove and hot-add PCI-X and PCIe cards.  Without pci=use_crs
a hot-add operation would have previously caused a machine check.

   Tested-by: Gary Hade <garyhade@...ibm.com>

Gary

-- 
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503  IBM T/L: 775-4503
garyhade@...ibm.com
http://www.ibm.com/linux/ltc

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