RE: [Qemu-devel] Re: [PATCH 2/4] move CPUID_APIC flag to where it belongs

[Stanislav]

Local apic and i/o apic are not really related.
Local apic is actually a cpu feature, not optional external peripheral.
I/O apic is external hardware on board and if you don't have it - you can't
program your interrupts that much.
I am not telling if a patch is wrong/better than it was before - just want
to point out how it really works.

Stanislav


-----Original Message-----
From: Glauber Costa [mailto:address@hidden 
Sent: Wednesday, May 06, 2009 8:42 PM
To: Stanislav
Cc: 'Jan Kiszka'; address@hidden; address@hidden
Subject: Re: [Qemu-devel] Re: [PATCH 2/4] move CPUID_APIC flag to where it
belongs

On Wed, May 06, 2009 at 08:29:23PM +0300, Stanislav wrote:
> If OS boot fine its more luck. The flag indicates presence of local apic,
> not "if it is supported".
> For example when lapic is globally disabled (i.e. not present) CPUID flag
is
> cleared off as well.
> But CPU is still supports lapic, after reset it will be back.
What if we take out a cpu that supports lapic, and is connected to an apic
system,
and connects it to a board that has no apic?

Also, note that in the old code, it was set regardless of the existance of
an APIC
anyway. The only dependancy was on smp_cpus > 1.