linux-kernel - [PATCH] i386/bigsmp: eliminate false warnings regarding logical APIC ID mismatches

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Date:	Thu, 15 Sep 2011 09:30:00 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<stable@...nel.org>, <tj@...nel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] i386/bigsmp: eliminate false warnings regarding
	 logical APIC ID mismatches

These warnings (generally one per CPU) are a result of initializing
x86_cpu_to_logical_apicid while apic_default is still in use, but the
check in setup_local_APIC() being done when apic_bigsmp was already
used as an override in default_setup_apic_routing():

Overriding APIC driver with bigsmp
Enabling APIC mode:  Physflat.  Using 5 I/O APICs
------------[ cut here ]------------
WARNING: at .../arch/x86/kernel/apic/apic.c:1239 setup_local_APIC+0x137/0x46b()
Hardware name: ...
CPU0 logical APIC ID: 1 != 0
Pid: 1, comm: swapper Not tainted 3.0.1-2011-08-09-jb #2
Call Trace:
 [<c1005f91>] try_stack_unwind+0x1b1/0x1f0
 [<c1004cc7>] dump_trace+0x47/0x110
 [<c1005b0b>] show_trace_log_lvl+0x4b/0x60
 [<c1005b38>] show_trace+0x18/0x20
 [<c1261435>] dump_stack+0x6d/0x72
 [<c10355f7>] warn_slowpath_common+0x77/0xb0
 [<c10356c3>] warn_slowpath_fmt+0x33/0x40
 [<c13fda81>] setup_local_APIC+0x137/0x46b
 [<c13d1733>] native_smp_prepare_cpus+0x108/0x1cd
 [<c13c61ff>] kernel_init+0x37/0x12c
 [<c1264826>] kernel_thread_helper+0x6/0xd
---[ end trace 4eaa2a86a8e2da22 ]---
...
CPU 1 irqstacks, hard=f1c9a000 soft=f1c9c000
Booting Node   0, Processors  #1
smpboot cpu 1: start_ip = 9e000
Initializing CPU#1
------------[ cut here ]------------
WARNING: at .../arch/x86/kernel/apic/apic.c:1239 setup_local_APIC+0x137/0x46b()
Hardware name: ...
CPU1 logical APIC ID: 2 != 8
...

Fix this (for the time being, i.e. until x86_32_early_logical_apicid()
will get removed again, as Tehun says ought to be possible) by
overriding the previously stored values at the point where the APIC
driver gets overridden.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Acked-by: Tejun Heo <tj@...nel.org>
Cc: stable@...nel.org (2.6.39 and onwards)

---
 arch/x86/kernel/apic/probe_32.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- 3.1-rc6/arch/x86/kernel/apic/probe_32.c
+++ 3.1-rc6-i386-bigsmp-early-lapicid-override/arch/x86/kernel/apic/probe_32.c
@@ -203,7 +203,18 @@ void __init default_setup_apic_routing(v
 	if (!cmdline_apic && apic == &apic_default) {
 		struct apic *bigsmp = generic_bigsmp_probe();
 		if (bigsmp) {
+			unsigned int cpu;
+
 			apic = bigsmp;
+			for_each_possible_cpu(cpu) {
+				if (early_per_cpu(x86_cpu_to_logical_apicid,
+						  cpu) == BAD_APICID)
+					continue;
+				early_per_cpu(x86_cpu_to_logical_apicid,
+					      cpu) =
+					bigsmp->x86_32_early_logical_apicid
+						(cpu);
+			}
 			printk(KERN_INFO "Overriding APIC driver with %s\n",
 			       apic->name);
 		}



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