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Re: [Xen-devel] [PATCH] qemu-xen: fix cpu hotplug

To: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] qemu-xen: fix cpu hotplug
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Thu, 2 Sep 2010 18:30:01 +0100
Cc: "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Li, Xin" <xin.li@xxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
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Stefano Stabellini writes ("[Xen-devel] [PATCH] qemu-xen: fix cpu hotplug"):
> qemu-xen: fix cpu hotplug
> The current xenstore watch path for a vcpu-set event is wrong and is
> also wrong the code to parse it.  This patch fixes both of them:

Thanks.  So it seems you're saying it's completely broken in

I have CC'd a bunch of Intel folks who were doing some other
work on cpu hotplug.  They were dealing with a race when multiple CPUs
were added at once.

So I think there must be some confusion.  Perhaps xl and xend have
different ideas about what the xenstore syntax is for these operations ?

Jinsong Liu et al: would you care to comment ?  Particularly about this:

> A xenstore vcpu hotplug command is of the following form:
> path: /local/domain/DOMID/cpu/VCPU_NUMBER/availability
> values: "online" or "offline"

That doesn't seem to match up with what's in xend, which seems to
write "cpu_avail" in the vm tree.


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