Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id

Yinghai Lu
2009-08-25T19:19:09Z

Ingo Molnar wrote:
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
>> On Tue, 25 Aug 2009, Yinghai Lu wrote:
>>> initial apic id and apic id could be different.
>>>
>>> and we should use initial apic id to get correct phys pkg id in
>>> case BIOS set crazy apic id.
>> Yinghai - I think you missed Cyrills' point. Let me repeat it:
>>
>> "cpu_has_apic bit turned off"
>>
>> there's no apic. No "initial apic id". No "phys pkg id". No
>> nothing.
>>
>> Discussions about "correct phys pkg id" are pointless.
>
> that's not the case here though:
>
> [ 8.713916] Total of 32 processors activated (162314.96 BogoMIPS).
>
> so APICs are active. The real difference is i think this aspect of
> commit 2759c3287:
>
> static int flat_phys_pkg_id(int initial_apic_id, int index_msb)
> {
> - return hard_smp_processor_id() >> index_msb;
> + return initial_apic_id >> index_msb;
> }
>
> We need to revert back to .30 behavior here. (In case of which
> environment to trust we almost always trust whatever booted millions
> of Linux boxes in the past already.)
>
> Furthermore, commit 2759c3287 did not declare any side-effects and
> clearly causes a side-effect on vSMP which apparently has an
> overlapping set of initial APIC ids.
>
> Ravikiran, your patch does not do a clear revert of this bit though.
> If you do a plain revert of the line above alone, does that fix the
> problem too?

how about patch phys_pkg_id for vsmp?

diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index f3b1037..65edc18 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -44,6 +44,11 @@ static struct apic *apic_probe[] __initdata = {
NULL,
};

+static int apicid_phys_pkg_id(int initial_apic_id, int index_msb)
+{
+ return hard_smp_processor_id() >> index_msb;
+}
+
/*
* Check the APIC IDs in bios_cpu_apicid and choose the APIC mode.
*/
@@ -69,6 +74,11 @@ void __init default_setup_apic_routing(void)
printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
}

+ if (is_vsmp_box()) {
+ /* need to update phys_pkg_id */
+ apic->phys_pkg_id = apicid_phys_pkg_id;
+ }
+
/*
* Now that apic routing model is selected, configure the
* fault handling for intr remapping.