Re: [PATCH][2.4.22-rc2] Disable APIC on reboot.

[Mikael Pettersson]

On Fri, 15 Aug 2003 21:22:10 +0200, Marc-Christian Petersen wrote:
>> disable_local_APIC() now checks if detect_init_APIC() enabled the
>> local APIC via the APIC_BASE MSR, and if so it now disables APIC_BASE.
>> Previously we would leave APIC_BASE enabled, and that made some
>> BIOSen unhappy.
>> The SMP reboot code calls disable_local_APIC(). On SMP HW there is
>> no change since detect_init_APIC() isn't called and APIC_BASE isn't
>> enabled by us. An SMP kernel on UP HW behaves just like an UP_APIC
>> kernel, so it disables APIC_BASE if we enabled it at boot.
>> The UP_APIC disable-before-suspend code is simplified since the existing
>> code to disable APIC_BASE is moved into disable_local_APIC().
>> (Felix Kühling originally reported the BIOS reboot problem. This is a
>> fixed-up version of his preliminary patch.)
>
>please correct me if I say something really stupid now but shouldn't the APIC 
>be disabled only during reboot time and enabled again at a new boot?
>
>my experience with this patch is, after a reboot he APIC isn't enabled again 
>until I power off my machine.

Seems impossible to me. We _know_ how to enable APIC_BASE,
otherwise this code wouldn't trigger at all.
Please give evidence as to what goes wrong, i.e., dmesg logs
from first (cold) and subsequent (warm) boots.
(Preferably from a standard 2.4.22-rc2 so I can verify the code.)

/Mikael
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