linux-kernel - Re: [PATCH 1/3] KVM: LAPIC: Extract adaptive tune timer advancement logic

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Date:   Mon, 13 May 2019 12:39:40 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH 1/3] KVM: LAPIC: Extract adaptive tune timer advancement
 logic

On Thu, May 09, 2019 at 07:29:19PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Extract adaptive tune timer advancement logic to a single function.

Why?

> 
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
> Cc: Liran Alon <liran.alon@...cle.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>  arch/x86/kvm/lapic.c | 57 ++++++++++++++++++++++++++++++----------------------
>  1 file changed, 33 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index bd13fdd..e7a0660 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1501,11 +1501,41 @@ static inline void __wait_lapic_expire(struct kvm_vcpu *vcpu, u64 guest_cycles)
>  	}
>  }
>  
> -void wait_lapic_expire(struct kvm_vcpu *vcpu)
> +static inline void adaptive_tune_timer_advancement(struct kvm_vcpu *vcpu,
> +				u64 guest_tsc, u64 tsc_deadline)
>  {
>  	struct kvm_lapic *apic = vcpu->arch.apic;
>  	u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns;
> -	u64 guest_tsc, tsc_deadline, ns;
> +	u64 ns;
> +
> +	if (!apic->lapic_timer.timer_advance_adjust_done) {
> +			/* too early */
> +			if (guest_tsc < tsc_deadline) {
> +				ns = (tsc_deadline - guest_tsc) * 1000000ULL;
> +				do_div(ns, vcpu->arch.virtual_tsc_khz);
> +				timer_advance_ns -= min((u32)ns,
> +					timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
> +			} else {
> +			/* too late */
> +				ns = (guest_tsc - tsc_deadline) * 1000000ULL;
> +				do_div(ns, vcpu->arch.virtual_tsc_khz);
> +				timer_advance_ns += min((u32)ns,
> +					timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
> +			}
> +			if (abs(guest_tsc - tsc_deadline) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
> +				apic->lapic_timer.timer_advance_adjust_done = true;
> +			if (unlikely(timer_advance_ns > 5000)) {
> +				timer_advance_ns = 0;
> +				apic->lapic_timer.timer_advance_adjust_done = true;
> +			}
> +			apic->lapic_timer.timer_advance_ns = timer_advance_ns;
> +		}

This whole block is indented too far.

> +}
> +
> +void wait_lapic_expire(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_lapic *apic = vcpu->arch.apic;
> +	u64 guest_tsc, tsc_deadline;
>  
>  	if (apic->lapic_timer.expired_tscdeadline == 0)
>  		return;
> @@ -1521,28 +1551,7 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu)
>  	if (guest_tsc < tsc_deadline)
>  		__wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
>  
> -	if (!apic->lapic_timer.timer_advance_adjust_done) {
> -		/* too early */
> -		if (guest_tsc < tsc_deadline) {
> -			ns = (tsc_deadline - guest_tsc) * 1000000ULL;
> -			do_div(ns, vcpu->arch.virtual_tsc_khz);
> -			timer_advance_ns -= min((u32)ns,
> -				timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
> -		} else {
> -		/* too late */
> -			ns = (guest_tsc - tsc_deadline) * 1000000ULL;
> -			do_div(ns, vcpu->arch.virtual_tsc_khz);
> -			timer_advance_ns += min((u32)ns,
> -				timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
> -		}
> -		if (abs(guest_tsc - tsc_deadline) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
> -			apic->lapic_timer.timer_advance_adjust_done = true;
> -		if (unlikely(timer_advance_ns > 5000)) {
> -			timer_advance_ns = 0;
> -			apic->lapic_timer.timer_advance_adjust_done = true;
> -		}
> -		apic->lapic_timer.timer_advance_ns = timer_advance_ns;
> -	}
> +	adaptive_tune_timer_advancement(vcpu, guest_tsc, tsc_deadline);
>  }
>  
>  static void start_sw_tscdeadline(struct kvm_lapic *apic)
> -- 
> 2.7.4
>