Re: Kernel 2.66.33-rC1 boot problem bisected to commit 99935a7a59eaca0292c1a5880e10bae03f4a5e3d

From: Yinghai Lu
Date: Sat Dec 19 2009 - 16:38:32 EST

Vincent ETIENNE wrote:
> I am experiencing boot problem with kernel 2.6.33-rc1. Bisection points to
> commit 99935a7a59eaca0292c1a5880e10bae03f4a5e3d
> Author: Yinghai Lu <yinghai@xxxxxxxxxx>
> Date: Sun Oct 4 21:54:24 2009 -0700
> x86/PCI: read root resources from IOH on Intel
> For intel systems with multi IOH, we should read peer root resources
> directly from PCI config space, and don't trust _CRS.
> Signed-off-by: Yinghai Lu <>
> Signed-off-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
> V2.6.32 is OK
> V2.6.33 is bad. A brief summary of the problem is that very quickly kernel (
> less than 1.5 seconds) try to mount the root device without doing any probing
> on disk leading to a kernel panic ( could not mount root devices). Alsa
> devices and usb devices is also not detected / not probed. Maybe other devices
> is also not detected but that just from the message seen on the monitor before
> the panic so it's not very accurate (no log as it doesn't boot and only one
> computer so no serial console). Sounds like the kernel didn't see any devices
> (disk, usb, sounds).
> I have a intel system so the commit log seems possibly relevant for the my
> computer (Not sure of what is IOH, i have take it for I/O Hub in the lspci out
> output and i have 3 of these according to lspci).
> Have try to revert the commit on a 2.6.33_rc1 base but this lead to some
> compilation problem (symbol not defined and so on). So I'm not completely sure
> of my bisection (also note that it's the first time i use git so an error is
> very possible).
> Attached a dmesg log with kernel 2.6.32-rc8 and lspci -vvv output.
> If you need further information/testing, i will my best to provide these.

please check

Subject: [PATCH 1/7] x86/pci: intel ioh bus num reg accessing fix

it is above 0x100, so if mmconf is not enable, need to skip it

Reported-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

arch/x86/pci/intel_bus.c | 4 ++++
1 file changed, 4 insertions(+)

Index: linux-2.6/arch/x86/pci/intel_bus.c
--- linux-2.6.orig/arch/x86/pci/intel_bus.c
+++ linux-2.6/arch/x86/pci/intel_bus.c
@@ -49,6 +49,10 @@ static void __devinit pci_root_bus_res(s
u64 mmioh_base, mmioh_end;
int bus_base, bus_end;

+ /* some sys doesn't get mmconf enabled */
+ if (dev->cfg_size < 0x200)
+ return;
if (pci_root_num >= PCI_ROOT_NR) {
printk(KERN_DEBUG "intel_bus.c: PCI_ROOT_NR is too small\n");

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