linux-kernel - Re: [PATCH v2 41/43] KVM: VMX: Pass desired vector instead of bool for triggering posted IRQ

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Date:   Mon, 01 Nov 2021 00:25:25 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Anup Patel <anup.patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Atish Patra <atish.patra@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 41/43] KVM: VMX: Pass desired vector instead of bool
 for triggering posted IRQ

On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Refactor the posted interrupt helper to take the desired notification
> vector instead of a bool so that the callers are self-documenting.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 78c8bc7f1b3b..f505fee3cf5c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3928,11 +3928,9 @@ static void vmx_msr_filter_changed(struct kvm_vcpu *vcpu)
>  }
>  
>  static inline bool kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu,
> -						     bool nested)
> +						     int pi_vec)
>  {
>  #ifdef CONFIG_SMP
> -	int pi_vec = nested ? POSTED_INTR_NESTED_VECTOR : POSTED_INTR_VECTOR;
> -
>  	if (vcpu->mode == IN_GUEST_MODE) {
>  		/*
>  		 * The vector of interrupt to be delivered to vcpu had
> @@ -3986,7 +3984,7 @@ static int vmx_deliver_nested_posted_interrupt(struct kvm_vcpu *vcpu,
>  		 */
>  		kvm_make_request(KVM_REQ_EVENT, vcpu);
>  		/* the PIR and ON have been set by L1. */
> -		if (!kvm_vcpu_trigger_posted_interrupt(vcpu, true))
> +		if (!kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_NESTED_VECTOR))
>  			kvm_vcpu_wake_up(vcpu);
>  		return 0;
>  	}
> @@ -4024,7 +4022,7 @@ static int vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
>  	 * guaranteed to see PID.ON=1 and sync the PIR to IRR if triggering a
>  	 * posted interrupt "fails" because vcpu->mode != IN_GUEST_MODE.
>  	 */
> -	if (!kvm_vcpu_trigger_posted_interrupt(vcpu, false))
> +	if (!kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_VECTOR))
>  		kvm_vcpu_wake_up(vcpu);
>  
>  	return 0;

I both like and don't like this patch.

It is indeed a bit more more self documented, but then it allows caller to
pass anything other than POSTED_INTR_NESTED_VECTOR/POSTED_INTR_VECTOR which
would fail.

Maybe addd an assert?

I won't do bikesheddding about this though, so

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky