linux-kernel - [PATCH] x86/amd: don't probe for extended APIC ID if APICs are disabled

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Message-ID: <4A674577.4020206@goop.org>
Date:	Wed, 22 Jul 2009 09:59:35 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Bastian Blank <bastian@...di.eu.org>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com
Subject: [PATCH] x86/amd: don't probe for extended APIC ID if APICs are disabled

If we've logically disabled apics, don't probe the PCI space for the
AMD extended APIC ID.

[ Impact: prevent boot crash under Xen. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Reported-by: Bastian Blank <bastian@...di.eu.org>

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 28e5f59..e2485b0 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -356,7 +356,7 @@ static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
 #endif
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_PCI)
 	/* check CPU config space for extended APIC ID */
-	if (c->x86 >= 0xf) {
+	if (cpu_has_apic && c->x86 >= 0xf) {
 		unsigned int val;
 		val = read_pci_config(0, 24, 0, 0x68);
 		if ((val & ((1 << 17) | (1 << 18))) == ((1 << 17) | (1 << 18)))


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