Re: cpu hotplug

[Gleb Natapov <gleb@redhat.com>]

On Sun, Sep 19, 2010 at 01:51:29PM +0200, Conrad Wood wrote:
> On Sun, 2010-09-19 at 13:39 +0200, Gleb Natapov wrote:
> > On Sun, Sep 19, 2010 at 01:32:28PM +0200, Conrad Wood wrote:
> > > On Sun, 2010-09-19 at 13:13 +0200, Gleb Natapov wrote:
> > > > On Sun, Sep 19, 2010 at 01:09:39PM +0200, Conrad Wood wrote:
> > > > > On Sun, 2010-09-19 at 12:46 +0200, Gleb Natapov wrote:
> > > > > [...]
> > > > > > > But... why does the command "info cpus" in the monitor report all cpus
> > > > > > > apart from CPU0 as (halted) ?
> > > > > > > 
> > > > > > Because they are halted? Run multiple cpu hogs in the guest and see if
> > > > > > cpus will still be halted as reported by monitor. Also kvm-72 is so
> > > > > > ancient that I am not sure it reports cpu state correctly in monitor at
> > > > > > all.
> > > > > > 
> > > > > > --
> > > > > fair enough, upgraded to 0.12.5, same results.
> > > > > 
> > > > > tried a cpu-hog (small loop forking 5 times and each fork doing some
> > > > > integer arithmetics for a while) - no change in info cpus
> > > > > 
> > > > > thank you, but I still don't get it ;-)
> > > > > 
> > > > At what rip are they halted? Try to run without kvm and see if the
> > > > result is the same. Can you provide output of "info cpus" here?
> > > > Are you using qemu-kvm or qemu BTW?
> > > 
> > > I am using qemu-kvm (debian package Version: 0.12.5+dfsg-3).
> > > Here's the "info cpus"  with and without kvm acceleration.
> > > basically qemu shows the behavior I'd expect, kvm does not. Or do I
> > > misunderstand something?
> > > 
> > No you are not. So your qemu-kvm version has cpu state reporting bug too. It is
> > not serious bug, just annoying. pc shows that otherwise everything is
> > working as expected.
> 
> I see. Is that a known bug, is someone working on that already?
> If not... could you point me to the relevant code sections/docs where I
> can fix that?
> It actually is quite relevant for me, as I have to manage quite a lot of
> VMs and need to be able to query how many cpus/cores they're using ;(
> 
I fixed it several times in the past[0][1][3], but it keeps re-appearing :) I
hope current qemu-kvm head is OK.

[0] 865aa3fec2b3d83c9b6edd452050a30ef6eaf3b8 
[1] 8c7d4cb7163d1c97df4439e2e0edb5918abf106b
[2] d6d233543d543fcf34df6190bbce5daf38d870f5

--
			Gleb.