2016-10-24 18:23+0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> Most windows guests still utilize APIC Timer periodic/oneshot mode
> instead of tsc-deadline mode, and the APIC Timer periodic/oneshot
> mode are still emulated by high overhead hrtimer on host. This patch
> converts the expected expire time of the periodic/oneshot mode to
> guest deadline tsc in order to leverage VMX preemption timer logic
> for APIC Timer tsc-deadline mode. After each preemption timer vmexit
> preemption timer is restarted to emulate LVTT current-count register
> is automatically reloaded from the initial-count register when the
> count reaches 0. This patch reduces ~5600 cycles for each APIC Timer
> periodic mode operation virtualization.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 117 ++++++++++++++++++++++++++++++++++++++-------------
> arch/x86/kvm/lapic.h | 1 +
> 2 files changed, 89 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> @@ -2005,8 +2060,12 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
>
> if (atomic_read(&apic->lapic_timer.pending) > 0) {
> kvm_apic_local_deliver(apic, APIC_LVTT);
> - if (apic_lvtt_tscdeadline(apic))
> + if (apic_lvtt_period(apic))
This should remain apic_lvtt_tscdeadline(). I can change that when
applying to kvm/queue.
> + apic->lapic_timer.tscdeadline = 0;
> + if (apic_lvtt_oneshot(apic)) {
> apic->lapic_timer.tscdeadline = 0;
> + apic->lapic_timer.target_expiration = ktime_set(0, 0);
> + }
> atomic_set(&apic->lapic_timer.pending, 0);
> }
> }
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