linux-kernel - Re: [PATCH] Make Intel 8-way Xeons boot again

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Date:	Mon, 11 Jan 2010 13:43:17 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	ananth@...ibm.com, suresh.b.siddha@...el.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>, stable@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: Re: [PATCH] Make Intel 8-way Xeons boot again

On Sun, Jan 10, 2010 at 2:26 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Yinghai Lu <yinghai@...nel.org> wrote:
>
>> On Sat, Jan 9, 2010 at 6:30 PM, Ananth N Mavinakayanahalli
>> <ananth@...ibm.com> wrote:
>> > On Sat, Jan 09, 2010 at 01:13:39PM -0800, Yinghai Lu wrote:
>> >> On Sat, Jan 9, 2010 at 2:10 AM, Ananth N Mavinakayanahalli
>> >> <ananth@...ibm.com> wrote:
>> >> > On an 8-way system with Intel Xeon X7350 CPUs, booting 2.6.32 or newer
>> >> > kernels fails at:
>> >> >
>> >> > ...
>> >> > CPU0: Intel(R) Xeon(R) CPU ? ? ? ? ? X7350 ?@ 2.93GHz stepping 0b
>> >> > Booting Node ? 0, Processors ?#1 #2 #3 #4 #5 #6 #7 Ok.
>> >> > Brought up 8 CPUs
>> >> > Total of 8 processors activated (46906.05 BogoMIPS).
>> >> >
>> >> > Git bisect showed 2fbd07a5f as the offending commit.
>> >> >
>> >> > With the patch below, I am able to boot the latest Linus' git tree on
>> >> > the machine. If this patch is correct, it needs to get into the stable
>> >> > tree too.
>> >> >
>> >> > Signed-off-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
>> >> > ---
>> >> > Index: linux-2.6/arch/x86/kernel/apic/probe_64.c
>> >> > ===================================================================
>> >> > --- linux-2.6.orig/arch/x86/kernel/apic/probe_64.c ? ? ?2010-01-09 14:54:29.000000000 +0530
>> >> > +++ linux-2.6/arch/x86/kernel/apic/probe_64.c ? 2010-01-09 14:57:53.000000000 +0530
>> >> > @@ -70,7 +70,7 @@
>> >> > ? ? ? ?if (apic == &apic_flat) {
>> >> > ? ? ? ? ? ? ? ?switch (boot_cpu_data.x86_vendor) {
>> >> > ? ? ? ? ? ? ? ?case X86_VENDOR_INTEL:
>> >> > - ? ? ? ? ? ? ? ? ? ? ? if (num_processors > 8)
>> >> > + ? ? ? ? ? ? ? ? ? ? ? if (num_processors >= 8)
>> >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?apic = &apic_physflat;
>> >> > ? ? ? ? ? ? ? ? ? ? ? ?break;
>> >> > ? ? ? ? ? ? ? ?case X86_VENDOR_AMD:
>> >>
>> >> can you send out whole bootlog with apic=debug?
>> >
>> > Here it is:
>> > ACPI: LAPIC (acpi_id[0x00] lapic_id[0x0c] enabled)
>> > ACPI: LAPIC (acpi_id[0x01] lapic_id[0x10] enabled)
>> > ACPI: LAPIC (acpi_id[0x02] lapic_id[0x0d] enabled)
>> > ACPI: LAPIC (acpi_id[0x03] lapic_id[0x11] enabled)
>> > ACPI: LAPIC (acpi_id[0x04] lapic_id[0x0e] enabled)
>> > ACPI: LAPIC (acpi_id[0x05] lapic_id[0x12] enabled)
>> > ACPI: LAPIC (acpi_id[0x06] lapic_id[0x0f] enabled)
>> > ACPI: LAPIC (acpi_id[0x07] lapic_id[0x13] enabled)
>> ...
>> > Setting APIC routing to flat
>> > Getting VERSION: 50014
>> > Getting VERSION: 50014
>> > Getting ID: c000000
>> > Getting ID: f3000000
>> > Getting LVT0: 700
>> > Getting LVT1: 400
>> > enabled ExtINT on CPU#0
>> > ESR value before enabling vector: 0x00000040 ?after: 0x00000000
>> > ENABLING IO-APIC IRQs
>> > ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
>> > CPU0: Intel(R) Xeon(R) CPU ? ? ? ? ? X7350 ?@ 2.93GHz stepping 0b
>> ...
>>
>> the BSP's physical apic id is 0x0c instead of 0.
>>
>> not sure Suresh test that or not.
>
> In any case this commit needs to be reverted as the assumption that it's safe
> to do this optimization is evidently not true.
>

use attached debug patch on one of my intel system and with nr_cpus=8,
it seems logical flat works.
that system BSP apic id is 0x20.

YH

View attachment "hard_maxcpus.patch" of type "text/x-diff" (2176 bytes)