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Date: Fri, 12 Dec 2014 19:42:18 +0100
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Subject: Re: [Qemu-devel] [PATCH] kvm/apic: fix 2.2->2.1 migration
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: imammedo@redhat.com, qemu-devel@nongnu.org



On 12/12/2014 18:30, Dr. David Alan Gilbert wrote:
> OK, let me just check that I get this....
> 
> It gets reset to 0 already in kvm_apic_realize

(before this patch -- after this patch it's only done in reset)

> then we do the common init

Then as part of starting up auxiliary processors we send an INIT
interrupt, that resets the APIC and...

> that sets it to !bsp - so 1 for most CPUs
> then you're adding this so that a specific APIC implementation (kvm)
> can nobble it back to 0 again?

Yes.  That's needed because this APIC implementation does not use the
field at all.

> and on the load side it's forced to zero by apic_pre_load.

Yes.  That's the common case for the !APIC implementation because it
gets to zero as soon as te OS starts.

Paolo