Hi,
I found the solution (or workaround only ?) to prevent from hanging up xenU
machines on a xen0 + BIOS HT enabled.
I must say I had another issue with the previous I described yesterday (see
thread).
I couldn't set up the max number of CPUs for my xen0 machine.
Whatever the "(dom0-cpus)" parameter value in my /etc/xen/xend-config.sxp
config file, I always had the following result in the "xm list" command
line:
> vn2:~# xm list
> Name ID Mem(MiB) VCPUs State Time(s)
> Domain-0 0 500 4 r----- 967.6
It was not possible for me to set up a max number value of CPUs on my dom0,
it was always set to the MAX (ie. 2 proc + HT enabled = 4 CPUs)
Thus, I added the following parameter in my GRUB/menus.lst config file:
"maxcpus=N"
example:
module /vmlinuz-2.6-xen0 root=/dev/sda3 ro maxcpus=3 console=tty0
max_loop=32
Then I rebooted.
... and suddenly my both problems where solved:
-1- I can limit my number of CPUs to a maximum value for xen0 and xenU
machines;
-2- My xenU stopped hanging up on boot !
(I must say it was not a kernel panic, but just a hang up... can't
explain it)
However, now I have some other inherent questions:
- I cannot set dynamically number of CPUs on my xen0 machine when it runs,
ie. the command "xm vcpu-set 0 N" doesn't work !
(whereas it works for xenU machines)
--> is it normal ?
is it possible in theory to change that number of CPUs on a running
xen0 ?
- What's the difference between (dom0-num-cpus) and (dom0-cpus) ?
Which one is really correct ?
Is it (dom0-num-cpus) for Xen2 and (dom0-cpus) for Xen3 ?
- Whatever the value I give to my "(dom0-cpus)" parameter in my
/etc/xen/xend-config.sxp file, it's totally unuseful... I really don't
know
what's the influence of this parameter to my machines ???
That's why I'm wondering whether I really found the solution to my previous
problem, or if it's only a workaround ?
Thank you,
Samuel
-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Samuel Torton
Sent: Tuesday, January 24, 2006 12:10 PM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] domU machines hang when Hyperthreading enabled in
BIOS
Hi,
I can't get rid of an annoying domU machines hanging issue with
Hyperthreading enabled in my BIOS.
Hardware config: IBM x325 series
2 * CPUs Intel Xeon 3.06 Ghz
Xen version: 3.0.0
Kernel version: 2.6.12.6
Linux distrib: Debian Sarge 3.1 r1
I run 1 domU machine on my dom0, here is my Xen config:
. xen0:
/etc/xen/xend-config.sxp : (dom0-num-cpus 0)
. xenU:
/etc/xen/myxenU.cfg : vcpus = 2
- First case: . BIOS Hyperthreading : DISABLED
. xen0 kernel config : SMT enabled
. xenU kernel config : SMT enabled or disabled (whatever)
When I reboot the physical machine, and run the command "xm list" :
. dom0 is visible and works fine
--> I see 2 cpus.
. domU is visible and works fine
--> I see 2 cpus;
I can console the xenU machine and work inside.
- Second case: . BIOS Hyperthreading : ENABLED
. xen0 kernel config : SMT enabled
. xenU kernel config : SMT enabled or disabled (whatever)
--> When I reboot the physical machine, and run the command "xm list" :
. dom0 is visible and works fine
--> I see 4 cpus.
. domU is visible and SEEMS to work fine (!)
--> I see 2 cpus;
If I console the xenU machine, I see the machine
has booted but is hanged before finishing the boot !!! :-(
Would you have any idea, any clue ? Do you have any experience ?
- Where to search in log files in order to detect the problem ?
- Which kernel parameter would I have forgotten ?
- I don't even know whether the problem comes from xen0 or xenU kernel
conf !
- etc... ?
Thank you in advance...
... please, don't advise me I have to disable Hyperthreading in BIOS !;-)
Regards,
Samuel
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