> Date: Sat, 15 Oct 2016 09:55:05 +0200 (CEST)
> From: s...@openbsd.org
> 
> On Fri, 14 Oct 2016, Mike Larkin wrote:
> 
> > On Fri, Oct 14, 2016 at 04:49:31PM +0900, YASUOKA Masahiko wrote:
> > > Hi,
> > > 
> > > I'm working on NEC Express5800/R110h-1 (dmesg is attached).  On this
> > > machine, our kernel panics with following message.
> > > 
> > >   cpu0 at mainbus0panic: cpu at apic id 0 already attached?
> > > 
> > > This seems to happen since x2APIC on the machine is enabled by BIOS
> > > and the kernel doesn't assume that.  The diff makes the kernel use
> > > x2APIC if it is enabled by BIOS.
> > > 
> > > ok?
> > > 
> > 
> > This should go in snaps, or wait for reports from tech@ with test results
> > before it should be committed, IMO. We don't have full support for x2apic,
> > and blindly enabling it like this hoping that the bios set everything up
> > right is bound to be a bad assumption on at least one machine out there.
> 
> As I understand the code, it should only change behavior on systems where 
> x2apic is enabled by the bios. And currently on such systems openbsd will 
> not work anyway, because we then try to use xapic mode without disabling 
> x2apic mode. Or am I missing something?

No, I think you're right and the risk of the diff is low.

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