RE: [Xen-devel] Genapic

["Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>]

I am a little confused here. When you say XenLinux I am assuming you are
talking about the Linux user kernels which have Xen patches. Why would
we even turn on the mach specific features in the user kernels?

I would think that that the mach specific code needs to reside in the
Xen hypervisor itself. It at the moment has unified apic.c/io_apic.c for
x86_32 and x86_64 platforms. Don't we to add genapic code in there? Or
am I wrong on this? Maybe I need more coffee :-)

Aravindh

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Nakajima,
Jun
Sent: Wednesday, May 18, 2005 1:22 PM
To: Andi Kleen; Keir Fraser
Cc: Subrahmanian, Raj; Davis, Jason; xen-devel@xxxxxxxxxxxxxxxxxxx;
Vessey, Bruce A
Subject: RE: [Xen-devel] Genapic

Andi Kleen wrote:
>> Shared platform code (apics and the like) has been remarkably simple.
>> This is to be expected:  processor differences aside, i386 and x86/64
>> are identical platforms. So, for example, fixing Xen's smpboot.c
> 
> No, they are not. x86-64 is a vastly simplified "modern x86 only with
> minimal bugs" platform, while i386 is a "workarounds for every bug
> under the sun and all ancient features plus some non PC architectures"
> mixed bag of stuff. This leads to many differences in details.
> 
> One bigger difference is that x86-64 is also normally NUMA enabled,
> while i386 normally is not. There are some others too.
> 
> -Andi
> 
I think in the long-term we want to have a unified code for
pic.c/io_apic.c in XenLinux, but we don't want to redo the dubugging and
testing that have already been done by Linux side (I know it's very
painful). We also want the same platform support in XenLinux as the
native Linux does; if we unify them today, we probably lose some
machines. This leads us to separate apic.c/io_apic.c for x86 and x86-64
XenLinux (that's the current plan), because debugging on various
platforms is more painful (even not realistic) than maintaining the
different code for x86 and x86-64 at this point. 

Jun

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