linux-kernel - Re: [PATCH 8/8] x86_64: Support for new UV apic

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Message-ID: <20080331022627.GE20619@sgi.com>
Date:	Sun, 30 Mar 2008 21:26:27 -0500
From:	Jack Steiner <steiner@....com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	tglx@...utronix.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] x86_64: Support for new UV apic

On Sun, Mar 30, 2008 at 07:23:07PM -0700, Yinghai Lu wrote:
> On Sun, Mar 30, 2008 at 7:12 PM, Jack Steiner <steiner@....com> wrote:
> > > >  Did you test it on non UV_X2APIC box?
> >  >
> >  > anyway the read_apic_id is totally wrong, even for your UV_X2APIC box.
> >  > because id=apic_read(APIC_ID) will have apic_id at bits [31,24], and
> >  > id |= __get_cpu_var(x2apic_extra_bits) is assuming that is on bits [5,0]
> >  >
> >  > so you even didn't test in your UV_X2APIC box!
> >  >
> >
> >  It works fine on UV_X2APIX boxes because the double shift does
> >  not occur. However, support for UV_X2APIC is dependent on
> >  x2apic code that is not yet in the tree. Once the APIC
> >  is switched into x2apic mode, the apicid is located in the LOW
> >  bits of the apicid register, not the HIGH bits.
> 
> oh, so that will need have new version GET_APIC_ID too.

Yes, although I think all the changes will be unified into
one non-inline function that is a combination of
GET_APIC_ID() & read_apic_id().

--- jack
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