Re: 2.6.27rc1 cannot boot more than 8CPUs

Ingo Molnar
2008-08-11T20:44:44Z

* Yinghai Lu <yhlu.kernel@gmail.com> wrote:

> [PATCH] x86: move def_to_bigsmp check later
>
> and skip the apicid id > 8

applied to tip/x86/urgent - thanks Yinghai. While we are touching this
code i cleaned up the printk a bit: the line breaking was way too ugly,
and the message not very informative about the effects of this problem.
See the full commit below.

Ingo

--------------->
>From b74548e76a0eab1f29546e7c5a589429c069a680 Mon Sep 17 00:00:00 2001
From: Yinghai Lu <yhlu.kernel@gmail.com>
Date: Mon, 11 Aug 2008 13:36:04 -0700
Subject: [PATCH] x86: fix 2.6.27rc1 cannot boot more than 8CPUs

Jeff Chua reported that booting a !bigsmp kernel on a 16-way box
hangs silently.

this is a long-standing issue, smp start AP cpu could check the
apic id >=8 etc before trying to start it.

achieve this by moving the def_to_bigsmp check later and skip the
apicid id > 8

[ mingo@elte.hu: clean up the message that is printed. ]

Reported-by: "Jeff Chua" <jeff.chua.linux@gmail.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/setup.c | 6 ------
arch/x86/kernel/smpboot.c | 10 ++++++++++
2 files changed, 10 insertions(+), 6 deletions(-)
---
arch/x86/kernel/setup.c | 6 ------
arch/x86/kernel/smpboot.c | 10 ++++++++++
2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 6e5823b..68b48e3 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -861,12 +861,6 @@ void __init setup_arch(char **cmdline_p)
init_apic_mappings();
ioapic_init_mappings();

-#if defined(CONFIG_SMP) && defined(CONFIG_X86_PC) && defined(CONFIG_X86_32)
- if (def_to_bigsmp)
- printk(KERN_WARNING "More than 8 CPUs detected and "
- "CONFIG_X86_PC cannot handle it.\nUse "
- "CONFIG_X86_GENERICARCH or CONFIG_X86_BIGSMP.\n");
-#endif
kvm_guest_init();

e820_reserve_resources();
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index da10f07..91055d7 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -994,7 +994,17 @@ int __cpuinit native_cpu_up(unsigned int cpu)
flush_tlb_all();
low_mappings = 1;

+#ifdef CONFIG_X86_PC
+ if (def_to_bigsmp && apicid > 8) {
+ printk(KERN_WARNING
+ "More than 8 CPUs detected - skipping them.\n"
+ "Use CONFIG_X86_GENERICARCH and CONFIG_X86_BIGSMP.\n");
+ err = -1;
+ } else
+ err = do_boot_cpu(apicid, cpu);
+#else
err = do_boot_cpu(apicid, cpu);
+#endif

zap_low_mappings();
low_mappings = 0;