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

Liu, Jinsong writes ("RE: [Xen-devel] [PATCH] qemu-xen: fix cpu hotplug"):
> Stabellini, I read your attached patch, it's OK. 

So we should apply Stefano's patch ?  I'm not sure I'm convinced.

> In fact, we firstly implemented xenstore watch by same scheme of
> your patch, watching each cpu node status:
> /local/domain/xx/cpu/yy/availability=offline (online)
> However, we finally didn't use this scheme. We watch 'common' node
> instead: /local/domain/xx/cpu in this way, only 1 watch point need.
> Considering vcpu number may become more and more in the future (say,
> more than 128), it's more simple and reasonable.  (Watches can be
> set at points in the hierarchy and an individual watch will be
> triggered when anything at or below that point in the hierachy
> changes)

Here you seem to be saying that the scheme that you implemented (in
xend, I take it) is not the same as the one in Stefano's patch.

> Yes, I think there must be some confusion.
> Currently 'xm vcpu-set' command works fine with both PV and HVM vcpu hotplug.

Right, good.

> Stabellini/Jackson, would your please tell me what xl recently
> happened for vcpu hotplug?

Well, we accepted patches to try to implement "xl vcpu-set" to make it
work like "xm vcpu-set" but they are apparently wrong.

>  is there any different ideas xl and xend about xenstore syntax?

xl should use the same syntax in xenstore as xend currently does.  If
xm (and therefore xend) and qemu currently work properly then changing
qemu will break xend.  Instead, libxl should be changed to use the
same scheme as xend.

> (Each time 'xm vcpu-set' executed, xend will write all xenstore cpu
> node status)



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