linux-kernel - Re: apic: native_apic_write

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Date:	Mon, 15 Jun 2009 00:06:20 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Simon Holm Thøgersen <odie@...aau.dk>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>
Subject: Re: apic: native_apic_write_dummy warning

[Cyrill Gorcunov - Sun, Jun 14, 2009 at 11:40:17PM +0400]
... 
| Neither thermal interrupts nor mce will be functional if apic
| is not properly set up (even having kernel compiled that way
| it support both). So you may try to pass "lapic" boot option
| and check if we're lucky in attempt to enable apic via force
| push. Anyway this warn show that the code is to be fixed
| (and native_apic_write_dummy done its work great catching
|  useless apic->write operation). I'll handle it but a bit later.
| 
| Andi CC'ed since he is involved in MCE handling just for the
| record.
| 
| 	-- Cyrill

Simon here is a patch I would appreciate if you test.

	-- Cyrill

---
[PATCH -tip] x86: mce intel -- don't touch THERMAL_APIC_VECTOR if no active APIC

If APIC was disabled for some reason and not even mapped
we should not try to enable thermal interrupts at all.

Reported-by: Simon Holm Thøgersen <odie@...aau.dk>
Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
---
 arch/x86/kernel/cpu/mcheck/mce_intel.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Index: linux-2.6.git/arch/x86/kernel/cpu/mcheck/mce_intel.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ linux-2.6.git/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -21,9 +21,15 @@ void intel_init_thermal(struct cpuinfo_x
 	int tm2 = 0;
 	u32 l, h;

-	/* Thermal monitoring depends on ACPI and clock modulation*/
-	if (!cpu_has(c, X86_FEATURE_ACPI) || !cpu_has(c, X86_FEATURE_ACC))
+	/*
+	 * Thermal monitoring depends on ACPI, clock modulation
+	 * and APIC as well
+	 */
+	if (!cpu_has(c, X86_FEATURE_ACPI) || !cpu_has(c, X86_FEATURE_ACC) ||
+		!cpu_has(c, X86_FEATURE_APIC)) {
+		pr_debug("Thermal monitoring disabled\n");
 		return;
+	}

 	/*
 	 * First check if its enabled already, in which case there might
--
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