From: James Cleverdon <jamesclv@us.ibm.com>
To: Andi Kleen <ak@muc.de>
Cc: YhLu <YhLu@tyan.com>, Matt Domsch <Matt_Domsch@dell.com>,
linux-kernel@vger.kernel.org, discuss@x86-64.org,
suresh.b.siddha@intel.com
Subject: Re: 256 apic id for amd64
Date: Fri, 7 Jan 2005 17:30:09 -0800 [thread overview]
Message-ID: <200501071730.09615.jamesclv@us.ibm.com> (raw)
In-Reply-To: <20050107122434.GA64665@muc.de>
Andi has already dealt with some of the coding style issues elsewhere in
the thread.
My comment: This is playing with fire. We've gone to considerable
trouble to make the boot_cpu_id independent of the physical APIC ID
(which is what hard_smp_processor_id() returns). Different BIOSes and
different CPU revisions can cause the boot processor to shift.
Examples: We have a box where the boot CPU has an APIC ID of 3.
Another system starts with the BSP == 3, but the BIOS renumbers it to
zero after first reassigning the original 0 CPU. So, the APIC IDs end
up 0, 1, 2, 4. Yet another system assigns the IDs: 0, 1, 6, 7.
We can expect even stranger numbering schemes in the future, given that
dual core hyperthreaded CPUs are in the pipeline. Creating any
dependency between CPU number and APIC ID is a _bad_ idea.
On Friday 07 January 2005 04:24 am, Andi Kleen wrote:
> On Thu, Jan 06, 2005 at 06:53:11PM -0800, YhLu wrote:
> > static unsigned int phys_pkg_id(int index_msb)
> > {
> > return hard_smp_processor_id() >> index_msb;
> > }
> >
> > In arch/x86_64/kernel/genapic_cluster.c
> >
> > Should be changed to
> >
> > static unsigned int phys_pkg_id(int index_msb)
> > {
> > /* physical apicid, so we need to substract offset */
> > return (hard_smp_processor_id() - boot_cpu_id) >>
> > index_msb; }
>
> Why?
>
> If you want a patch merged you need to supply some more explanation
> please.
>
> Also cc Suresh & James for comment.
>
> -Andi
--
James Cleverdon
IBM LTC (xSeries Linux Solutions)
{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot comm
next prev parent reply other threads:[~2005-01-08 1:36 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-07 2:53 256 apic id for amd64 YhLu
2005-01-07 12:24 ` Andi Kleen
2005-01-08 1:30 ` James Cleverdon [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-01-11 19:11 YhLu
2005-01-11 19:04 YhLu
2005-01-10 20:48 YhLu
2005-01-10 20:46 YhLu
2005-01-11 5:36 ` Andi Kleen
2005-01-10 20:37 YhLu
2005-01-10 20:09 YhLu
2005-01-10 20:18 ` Andi Kleen
2005-01-10 19:41 YhLu
2005-01-10 19:43 ` Andi Kleen
2005-01-11 0:42 ` James Cleverdon
2005-01-11 3:28 ` Siddha, Suresh B
2005-01-11 4:42 ` Andi Kleen
2005-01-10 18:48 YhLu
2005-01-10 18:45 ` Andi Kleen
2005-01-10 18:44 Andi Kleen
2005-01-11 4:04 ` Siddha, Suresh B
2005-01-11 4:39 ` Andi Kleen
2005-01-11 17:50 ` Andi Kleen
2005-01-08 2:53 YhLu
2005-01-09 23:56 ` James Cleverdon
2005-01-08 2:37 Mikael Pettersson
2005-01-08 15:46 ` Andi Kleen
2005-01-08 1:50 YhLu
2005-01-08 0:50 YhLu
2005-01-08 0:42 ` Andi Kleen
2005-01-08 0:28 YhLu
2005-01-08 0:26 ` James Cleverdon
2005-01-08 0:34 ` Andi Kleen
2005-01-08 0:04 YhLu
2005-01-08 0:12 ` James Cleverdon
2005-01-07 21:44 YhLu
2005-01-07 22:18 ` Andi Kleen
2005-01-07 21:14 YhLu
2005-01-07 21:12 ` Andi Kleen
2005-01-07 19:43 YhLu
2005-01-07 19:40 ` Andi Kleen
2005-01-07 18:27 YhLu
2005-01-07 19:29 ` Andi Kleen
2005-01-07 18:19 YhLu
2005-01-07 19:29 ` Andi Kleen
2005-01-07 1:06 YhLu
2005-01-07 12:44 ` Andi Kleen
2004-12-30 23:19 YhLu
2004-12-30 23:16 YhLu
2004-12-29 4:43 YhLu
2004-12-30 18:45 ` Andi Kleen
2004-12-30 22:56 ` Matt Domsch
2004-12-30 23:26 ` Andi Kleen
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