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Old 12-19-2008, 03:19 AM   #1
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Registered: Oct 2008
Posts: 12

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Xen: how to add VCPUs to windows guest

Hi all,

I have the latest RHEL 5.2 using XEN virtualization. I created several HVM windows w2k3 guests.

The issue is that I see only one CPU for each w2k3 guest. I configured the guest properly using parameter vcpus = 2

When i use xm I see that VCPUs are already allocated but the second one is paused:

[root@baranec xen]# xm vcpu-list
Name ID VCPUs CPU State Time(s) CPU Affinity
Domain-0 0 0 0 -b- 6110.4 0
Domain-0 0 1 1 -b- 415.1 1
Domain-0 0 2 2 -b- 527.8 2
Domain-0 0 3 3 r-- 790.4 3
Domain-0 0 4 4 -b- 368.4 4
Domain-0 0 5 5 -b- 454.9 5
Domain-0 0 6 6 -b- 370.1 6
Domain-0 0 7 7 -b- 273.9 7
cellmgr 21 0 7 -b- 2980.5 any cpu
cellmgr 21 1 - --p 0.0 any cpu
rohac 22 0 5 -b- 591.7 any cpu
rohac 22 1 - --p 0.0 any cpu

Maybe is the issue on side of W2k3 server.

Could you help me on this if there is some workaround?

Thank you very much.

Old 01-09-2009, 04:53 AM   #2
LQ Newbie
Registered: Oct 2008
Posts: 12

Original Poster
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Hi all,

I find the answer!

The problem is that official Red Hat Virtualization Guide recommends to select option Standard PC during installation of W2K3 guest. Windows than use HAL for common PC architecture and doesn't support multiple CPUs even you add them to guest by XEN.

To solve this issue you have to change HAL type and kernel to MPS Multiprocessor PC.

There is several way how to change it but most suitable way is to reinstall or remove HAL drivers.

How to change HAL by standard way on W2K3 guest:

- go to W2K3 guest's Control Panel / System / Device Manager / Computer and click on Standard PC item
- select Reinstall drivers to change HAL
- select MPS Multiprocessor PC
- restart guest

BUT I was not able to use this way because Windows reinstallation driver wizard didn't allow me to change drivers. Wizard tells me that he not find any better drivers and current drivers are working properly!!! (:-(o)

Finally I have to copy driver files manually and rename them:

- copy MPS files: halmps.dll, ntkrnlmp.exe and ntkrpamp.exe to <windows>\system32 folder
- rename MPS files using names of Standard PC drivers (replace them):
halmps.dll --> hal.dll
ntkrnlmp.exe --> ntoskrnl.exe
ntkrpamp.exe --> ntkrnlpa.exe
- restart the guest
- after restart Windows detects CPUs and compete installation of new hardware
- after the second restart everything goes OK

Good luck,
Old 01-09-2009, 10:31 AM   #3
Registered: Jun 2007
Posts: 118

Rep: Reputation: 16
How diferent is XEN virtualization from VMWARE?


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