linux-kernel - Re: [PATCH 2/2] KVM: s390: Use kvm_vcpu_wake_up in kvm_s390_vcpu

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Message-Id: <2af3fb79-61ae-d361-24d7-665cf9638e0b@de.ibm.com>
Date:   Thu, 18 Jul 2019 15:47:14 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     wanpengli@...cent.com, rkrcmar@...hat.com, paulus@...abs.org,
        maz@...nel.org
Subject: Re: [PATCH 2/2] KVM: s390: Use kvm_vcpu_wake_up in
 kvm_s390_vcpu_wakeup



On 18.07.19 15:37, Paolo Bonzini wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Use kvm_vcpu_wake_up() in kvm_s390_vcpu_wakeup().
> 
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
> 	v2->v3: no need to set vcpu->ready here
>  arch/s390/kvm/interrupt.c | 23 +++--------------------
>  1 file changed, 3 insertions(+), 20 deletions(-)

Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>

> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 26f8bf4a22a7..b5fd6e85657c 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1224,28 +1224,11 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
>  
>  void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu)
>  {
> -	/*
> -	 * We cannot move this into the if, as the CPU might be already
> -	 * in kvm_vcpu_block without having the waitqueue set (polling)
> -	 */
>  	vcpu->valid_wakeup = true;
> +	kvm_vcpu_wake_up(vcpu);
> +
>  	/*
> -	 * This is mostly to document, that the read in swait_active could
> -	 * be moved before other stores, leading to subtle races.
> -	 * All current users do not store or use an atomic like update
> -	 */
> -	smp_mb__after_atomic();
> -	if (swait_active(&vcpu->wq)) {
> -		/*
> -		 * The vcpu gave up the cpu voluntarily, mark it as a good
> -		 * yield-candidate.
> -		 */
> -		WRITE_ONCE(vcpu->ready, true);
> -		swake_up_one(&vcpu->wq);
> -		vcpu->stat.halt_wakeup++;
> -	}
> -	/*
> -	 * The VCPU might not be sleeping but is executing the VSIE. Let's
> +	 * The VCPU might not be sleeping but rather executing VSIE. Let's
>  	 * kick it, so it leaves the SIE to process the request.
>  	 */
>  	kvm_s390_vsie_kick(vcpu);
>