From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bei Guan <gbtju85@gmail.com>
Subject: Re: How does the Xen kernel change the vcpu number of a
	domain?
Date: Fri, 13 Jun 2014 22:36:25 +0800
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To: Wei Liu <wei.liu2@citrix.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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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">2014-06-13 16:59 GMT+08:00 Wei Liu <span dir=3D"ltr">&lt;<a href=3D=
"mailto:wei.liu2@citrix.com" target=3D"_blank">wei.liu2@citrix.com</a>&gt;<=
/span>:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div class=3D"">On Fri, Jun 13, 2014 at 03:1=
9:08PM +0800, Bei Guan wrote:<br>
&gt; Hi All,<br>
&gt;<br>
&gt; I try to figure out that how the command &quot;xl vcpu-set&quot; works=
. I find out<br>
&gt; that the command &quot;xl vcpu-set&quot; calls the method<br>
&gt; libxl__set_vcpuonline_xenstore() to set the state of the vcpu in the<b=
r>
&gt; Xenstore path /local/domain_id/cpu/vcpu_id/availability. The value of =
the<br>
&gt; key &quot;availability&quot; is set to &quot;online&quot; while the th=
e vcpu number will<br>
&gt; increase. When the key is set to &quot;offline&quot; the vcpu number w=
ill decrease.<br>
&gt;<br>
&gt; What I want to know is how does the vcpu number increase/decrease acco=
rding<br>
&gt; to the vcpu state in the Xenstore? =C2=A0How can I find the method tha=
t really<br>
&gt; does the work?<br>
&gt;<br>
<br>
</div>Linux kernel code drivers/xen/cpu_hotplug.c. It sets up a xenstore wa=
tch<br>
for &quot;cpu&quot; xenstore node and handles event accordingly.<br>
<br></blockquote><div>Thank you very much for your reply.</div><div>I&#39;m=
 using Xen-4.1.2. I also find that the Xen code tools/ioemu-qemu-xen/xensto=
re.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&=
#39;s difference between the two Xenstore watch in the Linux kernel and qem=
u-xen? Is the Xenstore watch in qemu-xen for HVM domains that are without P=
V drivers?</div>
<div><br></div><div>Thank you very much.</div><div><br></div><div>=C2=A0</d=
iv><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left=
:1px #ccc solid;padding-left:1ex">
Wei.<br>
<div class=3D""><br>
&gt; Any reply is appreciated. Thank you all very much.<br>
&gt;<br>
&gt; --<br>
&gt; Best Regards,<br>
&gt; Bei Guan<br>
<br>
</div>&gt; _______________________________________________<br>
&gt; Xen-devel mailing list<br>
&gt; <a href=3D"mailto:Xen-devel@lists.xen.org">Xen-devel@lists.xen.org</a>=
<br>
&gt; <a href=3D"http://lists.xen.org/xen-devel" target=3D"_blank">http://li=
sts.xen.org/xen-devel</a><br>
<br>
</blockquote></div><br><br clear=3D"all"><div><br></div>-- <br>Best Regards=
,<div>Bei Guan</div>
</div></div>

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