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Date: Sun, 30 Mar 2008 16:29:15 -0700
From: "Yinghai Lu" <yhlu.kernel@gmail.com>
To: "Andi Kleen" <andi@firstfloor.org>
Subject: Re: [RFC 8/8] x86_64: Support for new UV apic
Cc: "Jack Steiner" <steiner@sgi.com>, "Ingo Molnar" <mingo@elte.hu>,
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On Sun, Mar 30, 2008 at 2:18 PM, Andi Kleen <andi@firstfloor.org> wrote:
> > If there was a significant differece between UV and generic kernels
>  > (or hardware), then I would agree. However, the only significant
>  > difference is the APIC model on large systems. Small systems are
>  > exactly compatible.
>  >
>  > The problem with subarch is that we want 1 binary kernel to support
>
>  x86-64 subarchs are more options than true subarchs. They generally
>  do not prevent the kernel from running on other systems, just
>  control addition of some additional code or special data layout. They are
>  quite different from the i386 subarchs or those of other architectures.
>
>  The main reason vSMP is called a subarch is that it pads a lot
>  of data structures to 4K and you don't really want that on your
>  normal kernel, but there isn't anything in there that would
>  prevent booting on a normal system.
>
>  The UV option certainly doesn't have this issue.
>
>
>  > both generic hardware AND uv hardware. This restriction is desirable
>  > for the distros and software vendors. Otherwise, additional kernel
>  > images would have to be built, released, & certified.
>
>  I think an option would be fine, just don't call it a subarch. I don't
>  feel strongly about it, as you point out it is not really very much
>  code.

if the calling path like GET_APIC_ID is keeping checking if it is UV
box after boot time, that may not good.

don't need make other hundreds of machine keep running the code only
for several big box all the time.

YH
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