linux-kernel - [PATCH] lguest: fix TSC "divide error: 0000 [#1]" boot crash

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Message-Id: <1183080633.7803.10.camel@localhost.localdomain>
Date:	Fri, 29 Jun 2007 11:30:33 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Matt Mackall <mpm@...enic.com>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] lguest: fix TSC "divide error: 0000 [#1]" boot crash

Configuring a guest with < CONFIG_M586TSC reveals an lguest bug: the
TSC code expects to see the TSC capability bit, but we weren't setting
up the capabilities until much later in check_bugs ->
identify_boot_cpu -> identify_boot_cpu.

Do the same thing as Xen and the head.S native code: populate the
first capability word before start_kernel().

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r 7743cd1639b7 drivers/lguest/lguest.c
--- a/drivers/lguest/lguest.c	Thu Jun 28 23:21:41 2007 +1000
+++ b/drivers/lguest/lguest.c	Fri Jun 29 06:23:59 2007 +1000
@@ -598,6 +598,9 @@ __init void lguest_init(void *boot)
 	paravirt_disable_iospace();
 
 	cpu_detect(&new_cpu_data);
+	/* head.S usually sets up the first capability word, so do it here. */
+	new_cpu_data.x86_capability[0] = cpuid_edx(1);
+	
 	/* Math is always hard! */
 	new_cpu_data.hard_math = 1;
 


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