linux-kernel - Re: [PATCH v2 2/9] KVM: x86: remove return value of kvm_vcpu

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Date:   Wed, 17 Aug 2022 17:31:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        mlevitsk@...hat.com, vkuznets@...hat.com
Subject: Re: [PATCH v2 2/9] KVM: x86: remove return value of kvm_vcpu_block

On 8/17/22 01:34, Sean Christopherson wrote:
> Isn't freeing up the return from kvm_vcpu_check_block() unnecessary?  Can't we
> just do:
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9f11b505cbee..ccb9f8bdeb18 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10633,7 +10633,7 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
>                  if (hv_timer)
>                          kvm_lapic_switch_to_hv_timer(vcpu);
> 
> -               if (!kvm_check_request(KVM_REQ_UNHALT, vcpu))
> +               if (!kvm_arch_vcpu_runnable(vcpu))
>                          return 1;
>          }
> 
> 
> which IMO is more intuitive and doesn't require reworking halt-polling (again).

This was my first idea indeed.  However I didn't like calling 
kvm_arch_vcpu_runnable() again and "did it schedule()" seemed to be a 
less interesting result from kvm_vcpu_block() (and in fact 
kvm_vcpu_halt() does not bother passing it up the return chain).

Paolo