[PATCH RFC V3 0/6] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support

From: Wanpeng Li
Date: Thu Oct 13 2016 - 10:01:13 EST

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 MSR_IA32_TSCDEADLINE
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(-)