linux-kernel - Re: [tip:x86/urgent] x86: Detect use of extended APIC ID for AMD CPUs

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Message-ID: <20090608121805.GB8699@alberich.amd.com>
Date:	Mon, 8 Jun 2009 14:18:05 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86: Detect use of extended APIC ID for AMD
	CPUs

On Sun, Jun 07, 2009 at 11:46:51AM -0700, Yinghai Lu wrote:
> tip-bot for Andreas Herrmann wrote:
> > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> > index 42f2f83..9b2c049 100644
> > --- a/arch/x86/include/asm/apic.h
> > +++ b/arch/x86/include/asm/apic.h
> > @@ -410,7 +410,7 @@ static inline unsigned default_get_apic_id(unsigned long x)
> >  {
> >  	unsigned int ver = GET_APIC_VERSION(apic_read(APIC_LVR));
> >  
> > -	if (APIC_XAPIC(ver))
> > +	if (APIC_XAPIC(ver) || boot_cpu_has(X86_FEATURE_EXTD_APICID))
> >  		return (x >> 24) & 0xFF;
> >  	else
> >  		return (x >> 24) & 0x0F;
> 
> looks like we should fix APIC_XAPIC() or have one global apic_ver.

I thought to set the new flag for Intel as well and to replace
APIC_XAPIC with checks for that flag. But for some reason this was
ugly as lapic access must be configured before you can check the
APIC_VERSION and so I decided to keep Intel code as is and not to
potentially introduce regresions.


Regards,
Andreas


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