2017-06-23 17:22 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> Linux as a guest will prevent to program the next event to the clock event
> device when the event is in the past. However, it is not guaranteed by all
> the guests, the guest like kvm-unit-tests/apic.flat will write current tsc
> value visible in guest to MSR_IA32_TSCDEADLINE, lapic timer which is emulated
> by vmx preemption timer will program the absolute target tsc value to vmcs
> preemption timer field w/ delta == 0, then plays a vmentry and an upcoming
> vmx preemption timer fire vmexit dance, the lapic timer injection is delayed
> for this duration. Actually the lapic timer which is emulated by hrtimer can
> handle this correctly.
>
> This patch fixes it by firing the lapic timer and injecting a timer interrupt
> immediately during the next vmentry if guest programs an expired timer to
> the emulated timer device.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 6 +++++-
> arch/x86/kvm/vmx.c | 3 +++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index d24c874..8a1263a 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1504,12 +1504,16 @@ static void cancel_hv_timer(struct kvm_lapic *apic)
> static bool start_hv_timer(struct kvm_lapic *apic)
> {
> u64 tscdeadline = apic->lapic_timer.tscdeadline;
> + int ret = 0;
>
> if ((atomic_read(&apic->lapic_timer.pending) &&
> !apic_lvtt_period(apic)) ||
> - kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) {
> + (ret = kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline))) {
> if (apic->lapic_timer.hv_timer_in_use)
> cancel_hv_timer(apic);
> + if (ret == 1)
> + apic_timer_expired(apic);
> + return true;
Ouch! I just sent a wrong version.
Regards,
Wanpeng Li
> } else {
> apic->lapic_timer.hv_timer_in_use = true;
> hrtimer_cancel(&apic->lapic_timer.timer);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 2e906cf..2008e9b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11149,6 +11149,9 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
> u64 guest_tscl = kvm_read_l1_tsc(vcpu, tscl);
> u64 delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl;
>
> + if (delta_tsc == 0)
> + return 1;
> +
> /* Convert to host delta tsc if tsc scaling is enabled */
> if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio &&
> u64_shl_div_u64(delta_tsc,
> --
> 2.7.4
>
