Comment 0 for bug 1042612

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Michael Cook (michaelcook-mjc) wrote : KVM Guests only use one CPU after host wakes up from sleep

ThinkPad W520 running U12.04 with the latest updates applied.
VT-d enabled in BIOS
NVIDIA driver disabled (because it simply doesn't boot with VT-d enabled)
KVM Guests of Windows7, RHEL5.3

i) Start KVM Guest and you can see all host CPUs timeslicing and guest is fast and responsive.
ii) Shutdown KVM Guest.
iii) Place Host laptop into sleep mode.
iv) Wake up host and restart KVM Guest
v) KVM Guest CPU graph is at 50%, never fluctuates and behaviour is like single-core. All host CPUs are idling except for one at 100%.

This is quite reproducable. It is identical in performance and KVM Guest behaviour if you disabled VT-d in the BIOS (but have VT enabled).