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x86, x2apic: Preserve high 32-bits of IA32_APIC_BASE MSR 

If there's no special reason to zero-out the "high" 32-bits of the IA32_APIC_BASE
MSR, let's preserve it.

The x2APIC Specification doesn't explicitly state any such requirement. (Sec 2.2
in: http://www.intel.com/Assets/PDF/manual/318148.pdf).

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Link: http://lkml.kernel.org/r/20110712055831.2498.78521.sendpatchset@nchumbalkar.americas.cpqcorp.net
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Naga Chumbalkar 2011-07-12 05:59:07 +00:00 committed by H. Peter Anvin
parent 7fece83235
commit 2597085228
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/apic/apic.c
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@ -1429,7 +1429,7 @@ void enable_x2apic(void)
rdmsr(MSR_IA32_APICBASE, msr, msr2);
if (!(msr & X2APIC_ENABLE)) {
printk_once(KERN_INFO "Enabling x2apic\n");
wrmsr(MSR_IA32_APICBASE, msr | X2APIC_ENABLE, 0);
wrmsr(MSR_IA32_APICBASE, msr | X2APIC_ENABLE, msr2);
}
}
#endif /* CONFIG_X86_X2APIC */