linux-kernel - Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg

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Message-ID: <4A9438D1.4030608@kernel.org>
Date:	Tue, 25 Aug 2009 12:17:37 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Ravikiran G Thirumalai <kiran@...lex86.org>,
	linux-kernel@...r.kernel.org, shai@...lex86.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id

Ingo Molnar wrote:
> * Linus Torvalds <torvalds@...ux-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.
--
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