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RE: [Xen-devel] x86_64 SLES 9 SP2 build break

To: "Ryan Harper" <ryanh@xxxxxxxxxx>
Subject: RE: [Xen-devel] x86_64 SLES 9 SP2 build break
From: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Date: Fri, 19 Aug 2005 11:41:38 -0700
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, David F Barrera <dfbp@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Thread-topic: [Xen-devel] x86_64 SLES 9 SP2 build break
Ryan Harper wrote:
>>> You need x86_64 to run ASAP, not HOTPLUG_CPU for x86_64 smp,
>>> correct? 
>> No, we _do_ need HOTPLUG_CPU for x86_64 smp. The build problem is
>> not a big deal.
> Ah. OK.  I don't think it will be a problem for Xen, but currently in
> plain linux-2.6.13-rc6 (which has x86_64 HOTPLUG_CPU support),
> support is non-functional, at least on my two-way Opteron box.  I can
> remove a cpu (echo 0 > /sys/devices/system/cpu/cpu1/online) fine, but
> when I try to restore (echo 1), the processor fails to come back. 
> Part of this is that they are integrating the physical hotplug
> support which requires a full reboot of the processor (a second run
> through do_boot_cpu()) since it would have been physically removed.  
> I really wanted to see HOTPLUG_CPU work on plain Linux before
> bringing the code into XenLinux, but the issues may be tied up in
> code that Xen doesn't need.  The hypervisor will have to support
> physical hotplug before XenLinux will need it.

That's right. As long as we handle VCPU, that should be Xen-specific and
common between x86 and x86_64 (although smp.c & smpboot.c are slightly
different there at this point).

> There are some other subtle differences in HOTPLUG_CPU in the newer
> 2.6.13 series for x86_64 compared to the level of HOTPLUG_CPU we have
> patched into the 2.6.12 tree.
> I'll go ahead and work up a patch that brings in HOTPLUG_CPU for
> x86_64 and share that so we both can work on getting it working.


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