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Subject2.4.2[01] i386 does not reenable local apic
Date
Initial /proc/cpuinfo (Compaq Evo N800v).

processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Mobile Intel(R) Pentium(R) 4 - M CPU 2.00GHz
stepping : 7
cpu MHz : 1993.585
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts mmx fxsr sse sse2 ss ht tm
bogomips : 3971.48

arc/i386/kernel/apic.c::detect_init_APIC()

switch (boot_cpu_data.x86_vendor) {
case X86_VENDOR_AMD:
if (boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model > 1)
break;
if (boot_cpu_data.x86 == 15 && cpu_has_apic)
break;
goto no_apic;
case X86_VENDOR_INTEL:
if (boot_cpu_data.x86 == 6 ||
(boot_cpu_data.x86 == 15 && cpu_has_apic) ||
(boot_cpu_data.x86 == 5 && cpu_has_apic))
break;
goto no_apic;
default:
goto no_apic;
}
if (!cpu_has_apic) {
/*
* Some BIOSes disable the local APIC in the
* APIC_BASE MSR. This can only be done in
* software for Intel P6 and AMD K7 (Model > 1).
*/
rdmsr(MSR_IA32_APICBASE, l, h);
if (!(l & MSR_IA32_APICBASE_ENABLE)) {
printk("Local APIC disabled by BIOS -- reenabling.\n");
l &= ~MSR_IA32_APICBASE_BASE;
l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
wrmsr(MSR_IA32_APICBASE, l, h);
}
}
Because boot_cpu_data.x86 == 15 and the local APIC is disabled in BIOS,
detect_init_APIC() skips the code that reenables the local APIC. This
test is back to front. Change the code to force X86_VENDOR_INTEL to
drop through and it successfully reenables the local apic, I even get
NMI events.

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