Re: How does the Xen kernel change the vcpu number of a domain?

[Bei Guan <gbtju85@gmail.com>]

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2014-06-13 16:59 GMT+08:00 Wei Liu <wei.liu2@citrix.com>:

> On Fri, Jun 13, 2014 at 03:19:08PM +0800, Bei Guan wrote:
> > Hi All,
> >
> > I try to figure out that how the command "xl vcpu-set" works. I find out
> > that the command "xl vcpu-set" calls the method
> > libxl__set_vcpuonline_xenstore() to set the state of the vcpu in the
> > Xenstore path /local/domain_id/cpu/vcpu_id/availability. The value of the
> > key "availability" is set to "online" while the the vcpu number will
> > increase. When the key is set to "offline" the vcpu number will decrease.
> >
> > What I want to know is how does the vcpu number increase/decrease
> according
> > to the vcpu state in the Xenstore?  How can I find the method that really
> > does the work?
> >
>
> Linux kernel code drivers/xen/cpu_hotplug.c. It sets up a xenstore watch
> for "cpu" xenstore node and handles event accordingly.
>
> Thank you very much for your reply.
I'm using Xen-4.1.2. I also find that the Xen code
tools/ioemu-qemu-xen/xenstore.c sets a Xenstore watch for
/loca/domain/domid/cpu. It handles the watch event in the method
xenstore_procees_vcpu_set_event(char **vec). So, what's difference between
the two Xenstore watch in the Linux kernel and qemu-xen? Is the Xenstore
watch in qemu-xen for HVM domains that are without PV drivers?

Thank you very much.



> Wei.
>
> > Any reply is appreciated. Thank you all very much.
> >
> > --
> > Best Regards,
> > Bei Guan
>
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xen.org
> > http://lists.xen.org/xen-devel
>
>


-- 
Best Regards,
Bei Guan

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