[PATCH] [Intrepid SRU, Jaunty] x86: only scan the root bus in early PCI quirks
Tim Gardner
tim.gardner at canonical.com
Thu Mar 5 16:12:56 UTC 2009
Stefan Bader wrote:
> Tim Gardner wrote:
>> Stefan Bader wrote:
>>> 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...
>>>
>>
>> Unless someone has this specific problem (which would satisfy SRU
>> requirements), then I'd say apply it to the stable branch only.
>>
> There actually has been one. See
>
>> it seems that I was looking for that patch without knowing that I was
>> looking for that. ;-) This
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/267295 report
>> really sounds like the exact problem that is described, so I'll use
>> that for the SRU.
>
>
>
Well then, make it so.
--
Tim Gardner tim.gardner at canonical.com
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