[ kvm-Bugs-2988248 ] Windows XP x64 cannot use more than 2 cores

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Bugs item #2988248, was opened at 2010-04-16 15:46
Message generated for change (Tracker Item Submitted) made by ruclen
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Arseny Klimovsky (ruclen)
Assigned to: Nobody/Anonymous (nobody)
Summary: Windows XP x64 cannot use more than 2 cores

Initial Comment:
I'm using Ubuntu 9.10 with kernel 
2.6.31-20-generic #58-Ubuntu SMP Fri Mar 12 04:38:19 UTC 2010 x86_64 GNU/Linux
Processor
Intel(R) Core(TM) i7 CPU         975  @ 3.33GHz
4 cores, HyperThreading enabled, so in host linux I see 8 CPUs.
QEMU-KVM version:
qemu-kvm-0.11.0
I'm running guest Windows XP Pro x64 SP2
KVM command:
/usr/bin/kvm -S -M pc-0.11 -m 2048 -smp 8 -name virtual1 -uuid *** -monitor unix:/var/run/libvirt/qemu/virtual1.monitor,server,nowait -localtime -boot c -drive file=,if=ide,media=cdrom,index=0 -drive file=,if=ide,media=cdrom,index=2 -drive file=***/virtual1.img,if=virtio,index=0,boot=on -net nic,macaddr=***,vlan=0,model=virtio,name=virtio.0 -net tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb -usbdevice tablet -vnc 127.0.0.1:0 -k en-us -vga cirrus

Inside the VM in device manager I see 8 CPUs, but actually everything else make me think that only 2 cores are used:
1. In task manager I see 2 graphs for CPU load
2. One core application has 50% cpu load.
3. In host machine htop shows only 2 cores are loaded (when multiple heavy-load processes are run in VM).

If I use "-smp 4" instead of "-smp 8", the behavior is the same.
So, why I see such behavior?

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