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Re: [Xen-devel] RE: [PATCH] Allocate vmcs pages when system booting

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Yunhong Jiang <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] RE: [PATCH] Allocate vmcs pages when system booting
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 18 Mar 2010 10:51:36 +0000
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On 18/3/10 10:45, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>> In fact it's really not clear to me why cpu_possible_map must be set to
>>> CPU_MASK_ALL - if Linux has ways to avoid this, Xen should have too.
>> Does Linux manage a good reliable job of cutting down cpu_possible_map? That
>> would save cpu_possible_map in my eyes, if we could do that. Otherwise it is
>> indeed pretty useless now. Either way, I'd like cpu hotplug notifier chains
>> in the 4.1 development window.
> Only now got to look into this: Linux simply counts the disabled CPUs
> along with the present ones, plus it allows a command line override to
> the number of CPU slots reserved for hotplug. I just put together
> something similar, partly copying code over from there. Will submit
> post-4.0.

Intel are going to submit patches for cpu hotplug notifiers post-4.0, which
is the best solution. I think we can get rid of all possible_map uses in the

 -- Keir

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