linux-kernel - Re: [PATCH v2 42/43] KVM: VMX: Fold fallback path into triggering posted IRQ helper

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Date:   Mon, 01 Nov 2021 00:30:07 +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 42/43] KVM: VMX: Fold fallback path into triggering
 posted IRQ helper

On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Move the fallback "wake_up" path into the helper to trigger posted
> interrupt helper now that the nested and non-nested paths are identical.

Nit: I think you refer to patch 41 here, but I think that nested and non nested paths were identical
before as well, so this patch could be done without patch 41 as well.


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

Best regards,
	Maxim Levitsky


> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f505fee3cf5c..b0d97cf18c34 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3927,7 +3927,7 @@ static void vmx_msr_filter_changed(struct kvm_vcpu *vcpu)
>  	pt_update_intercept_for_msr(vcpu);
>  }
>  
> -static inline bool kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu,
> +static inline void kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu,
>  						     int pi_vec)
>  {
>  #ifdef CONFIG_SMP
> @@ -3958,10 +3958,15 @@ static inline bool kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu,
>  		 */
>  
>  		apic->send_IPI_mask(get_cpu_mask(vcpu->cpu), pi_vec);
> -		return true;
> +		return;
>  	}
>  #endif
> -	return false;
> +	/*
> +	 * The vCPU isn't in the guest; wake the vCPU in case it is blocking,
> +	 * otherwise do nothing as KVM will grab the highest priority pending
> +	 * IRQ via ->sync_pir_to_irr() in vcpu_enter_guest().
> +	 */
> +	kvm_vcpu_wake_up(vcpu);
>  }
>  
>  static int vmx_deliver_nested_posted_interrupt(struct kvm_vcpu *vcpu,
> @@ -3984,8 +3989,7 @@ 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, POSTED_INTR_NESTED_VECTOR))
> -			kvm_vcpu_wake_up(vcpu);
> +		kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_NESTED_VECTOR);
>  		return 0;
>  	}
>  	return -1;
> @@ -4022,9 +4026,7 @@ 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, POSTED_INTR_VECTOR))
> -		kvm_vcpu_wake_up(vcpu);
> -
> +	kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_VECTOR);
>  	return 0;
>  }
>