linux-kernel - Re: Possible x2apic breakage

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Date:	Thu, 29 Jan 2009 14:03:28 -0600
From:	Jack Steiner <steiner@....com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	suresh.b.siddha@...el.com, linux-kernel@...r.kernel.org
Subject: Re: Possible x2apic breakage

On Thu, Jan 29, 2009 at 05:15:46PM +0100, Ingo Molnar wrote:
> 
> * Jack Steiner <steiner@....com> wrote:
> 
> > Suresh -
> > 
> > This popped up in Ingo's x86 tree yesterday. This appears to be breaking
> > on our simulator running in x2apic mode. If I understand the code,
> > this is a real breakage and not a problem in our simulator:
> > 
> > 
> > arch/x86/include/asm/genapic.h
> > 
> > 	static inline unsigned int read_apic_id(void)
> > 	{
> >         	unsigned int reg;
> > 
> >         	reg = *(u32 *)(APIC_BASE + APIC_ID);
> >         	return apic->get_apic_id(reg);
> > 	}
> > 
> > 
> > As expected, the failure occurs right after:
> > 
> > 	Enabling x2apic
> > 	Enabled x2apic and interrupt-remapping
> > 
> > The next reference to apicid tries to read from mem instead of MSRs.
> 
> yes - Suresh sent a fix earlier today. Could you please check latest 
> tip/master (v2.6.29-rc3-1212-g69f3c6d or later), does it work fine in your 
> simulator?

That fixed it. The latest tree now runs our (very limited) regression suite
of tests on all apic modes.

Thanks...


--- jack
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