[PATCH] [Intrepid SRU, Jaunty] x86: only scan the root bus in early PCI quirks

[Stefan Bader]

Tim Gardner wrote:
> Yingying Zhao wrote:
>> SRU Justification:
>> We found a problem that on Tylersburg-HEDT with Nvidia Graphics card, system may result in kernel panic. Andi Kleen provided the patch to fix this problem. Please consider to include this patch in Jaunty and Intrepid.
>>
>> Patch (also attached):
>> --
>> commit 8659c406ade32f47da2c95889094801921d6330a
>> Author: Andi Kleen <andi at firstfloor.org>
>> Date:   Fri Jan 9 12:17:39 2009 -0800
>>
>>     x86: only scan the root bus in early PCI quirks
>>     
>>     We found a situation on Linus' machine that the Nvidia timer quirk hit on
>>     a Intel chipset system.  The problem is that the system has a fancy Nvidia
>>     card with an own PCI bridge, and the early-quirks code looking for any
>>     NVidia bridge triggered on it incorrectly.  This didn't lead a boot
>>     failure by luck, but the timer routing code selecting the wrong timer
>>     first and some ugly messages.  It might lead to real problems on other
>>     systems.
>>     
>>     I checked all the devices which are currently checked for by early_quirks
>>     and it turns out they are all located in the root bus zero.
>>     
>>     So change the early-quirks loop to only scan bus 0.  This incidently also
>>     saves quite some unnecessary scanning work, because early_quirks doesn't
>>     go through all the non root busses.
>>     
>>     The graphics card is not on bus 0, so it is not matched anymore.
>>     
>>     Signed-off-by: Andi Kleen <ak at linux.intel.com>
>>     Cc: Ingo Molnar <mingo at elte.hu>
>>     Cc: Thomas Gleixner <tglx at linutronix.de>
>>     Cc: "H. Peter Anvin" <hpa at zytor.com>
>>     Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
>>     Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
>>     Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
>>
>> diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
>> index 744aa7f..76b8cd9 100644
>> --- a/arch/x86/kernel/early-quirks.c
>> +++ b/arch/x86/kernel/early-quirks.c
>> @@ -201,6 +201,12 @@ struct chipset {
>>  	void (*f)(int num, int slot, int func);
>>  };
>>  
>> +/*
>> + * Only works for devices on the root bus. If you add any devices
>> + * not on bus 0 readd another loop level in early_quirks(). But
>> + * be careful because at least the Nvidia quirk here relies on
>> + * only matching on bus 0.
>> + */
>>  static struct chipset early_qrk[] __initdata = {
>>  	{ PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
>>  	  PCI_CLASS_BRIDGE_PCI, PCI_ANY_ID, QFLAG_APPLY_ONCE, nvidia_bugs },
>> @@ -267,17 +273,17 @@ static int __init check_dev_quirk(int num, int slot, int func)
>>  
>>  void __init early_quirks(void)
>>  {
>> -	int num, slot, func;
>> +	int slot, func;
>>  
>>  	if (!early_pci_allowed())
>>  		return;
>>  
>>  	/* Poor man's PCI discovery */
>> -	for (num = 0; num < 32; num++)
>> -		for (slot = 0; slot < 32; slot++)
>> -			for (func = 0; func < 8; func++) {
>> -				/* Only probe function 0 on single fn devices */
>> -				if (check_dev_quirk(num, slot, func))
>> -					break;
>> -			}
>> +	/* Only scan the root bus */
>> +	for (slot = 0; slot < 32; slot++)
>> +		for (func = 0; func < 8; func++) {
>> +			/* Only probe function 0 on single fn devices */
>> +			if (check_dev_quirk(0, slot, func))
>> +				break;
>> +		}
>>  }
>>
>>
>>
> 
> applied to Jaunty
> 

This is sort of nitpick, but I think formally I'd need at least one ack for 
Intrepid...

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