Most windows guests which I have on hand currently still utilize APIC Timer 
periodic/oneshot mode instead of APIC Timer tsc-deadline mode:
- windows 2008 server r2
- windows 2012 server r2
- windows 7
- windows 10 

This patchset adds the APIC Timer periodic/oneshot mode VMX preemption 
timer support.

I test the patchset by modifying kvm-unit-test/apic.flat to test 10w times 
APIC timer operations (from guest writes LVTT to timer fire and return to 

The patchset reduces ~300+ clock cycles for each APIC timer oneshot mode 
operation virtualization. However, the performance of periodic mode is 
still bad, so this version is still a RFC. Your comments to improve the 
patchset is a great appreciated.

v2 -> v3:
 * remove kvm_lapic_hv_timer_in_use() check in apic_get_tmcc, replace
   the hritmer_get_remaining() by target_expiration - now
 * rename expired_period to target_expiration
 * introduce set_target_expiration() helper
 * move the checking of minimal period to set_target_expiration()
 * cleanup kvm_get_lapic_target_deadline_tsc()

v1 -> v2:
 * remember the timeout when setting up the timer to get a correct TMCCT
 * move apic->lapic_timer.period/tscdeadline caculations to start_apic_timer()

Wanpeng Li (6):
  KVM: LAPIC: extract start_sw_period() to handle periodic/oneshot mode
  KVM: LAPIC: guarantee the timer is in tsc-deadline mode when rdmsr 
  KVM: LAPIC: introduce set_target_expiration to set target expiration time
  KVM: LAPIC: introduce kvm_get_lapic_target_expiration_tsc() to get APIC Timer 
target deadline tsc
  KVM: LAPIC: rename start/cancel_hv_tscdeadline to start/cancel_hv_timer
  KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support

 arch/x86/kvm/lapic.c | 173 +++++++++++++++++++++++++++++++--------------------
 arch/x86/kvm/lapic.h |   2 +
 arch/x86/kvm/x86.c   |   2 +-
 3 files changed, 109 insertions(+), 68 deletions(-)


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