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Re: [Qemu-devel] [PATCH 11/19] target-i386: introduce apic-id property

From: Eduardo Habkost
Subject: Re: [Qemu-devel] [PATCH 11/19] target-i386: introduce apic-id property
Date: Mon, 15 Apr 2013 10:45:24 -0300
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Apr 15, 2013 at 03:37:00PM +0200, Igor Mammedov wrote:
> > > > ID to be directly specified in the device_add/-device options.  That's
> > > > how real CPUs work: as the CPU manufacturer doesn't know what will be
> > > > the package ID of the CPU, the APIC IDs are not hardcoded in the CPU;
> > > > they are calculated based on the CPU topology and some socket identifier
> > > > signal coming from the board.
> > > that is why apic_id has been made a property, to be set from outside.
> > 
> > True. I believe the conflict here is: we want other objects to set the
> > APIC ID (be it the board, or socket/core objects), but at the same time
> > it would be interesting to not expose the APIC ID outside QEMU. Being
> > too flexible regarding the APIC ID is more likely to cause problems
> > later.
> > 
> > That said, I don't mind having a "apic-id" property because it is easier
> > to simply expose it directly. But do you agree that: 1) we don't really
> > need to expose it to be set from outside QEMU; 2) we shouldn't require
> > it to be set from outside QEMU; 3) we should recommend users to not try
> > to fiddle it with?
> Due to nature of per thread CPU hotplug, management will have to specify some
> kind of ID to specify which CPU is being plugged. Management really
> doesn't/shouldn't care what this ID is.

As long as management really doesn't/shouldn't care what the ID is,
exposing the APIC ID in the form of an opaque CPU identifier wouldn't be
a problem to me. I just wanted to make clarify if we agree that messing
with the APIC ID directly won't be recommended and that the "apic-id"
property will be for QEMU internal use only.


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