linux-kernel - Re: [PATCH] KVM: LAPIC: Reset timer_advance_ns to 1000 after adaptive tuning goes insane

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Message-ID: <dfdce82d-7cea-9b8d-0187-906b777d494d@redhat.com>
Date:   Fri, 5 Jul 2019 11:50:45 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: LAPIC: Reset timer_advance_ns to 1000 after adaptive
 tuning goes insane

On 05/07/19 11:40, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Reset timer_advance_ns to the default value 1000ns after adaptive tuning 
> goes insane which can happen sporadically in product environment.
> 
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>  arch/x86/kvm/lapic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 05d8934..454d3dd 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1549,7 +1549,7 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu,
>  	if (abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
>  		apic->lapic_timer.timer_advance_adjust_done = true;
>  	if (unlikely(timer_advance_ns > 5000)) {
> -		timer_advance_ns = 0;
> +		timer_advance_ns = 1000;
>  		apic->lapic_timer.timer_advance_adjust_done = true;

Do you also want to reset timer_advance_adjust_done to false?

Paolo

>  	}
>  	apic->lapic_timer.timer_advance_ns = timer_advance_ns;
>