linux-kernel - Re: [PATCH] KVM: x86: async_pf: check earlier if can deliver async pf

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Message-ID: <Z0CWAXqMl-wTdGXm@google.com>
Date: Fri, 22 Nov 2024 06:32:33 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kalyazin@...zon.com, pbonzini@...hat.com, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, david@...hat.com, 
	peterx@...hat.com, oleg@...hat.com, gshan@...hat.com, graf@...zon.de, 
	jgowans@...zon.com, roypat@...zon.co.uk, derekmn@...zon.com, nsaenz@...zon.es, 
	xmarcalx@...zon.com
Subject: Re: [PATCH] KVM: x86: async_pf: check earlier if can deliver async pf

On Fri, Nov 22, 2024, Vitaly Kuznetsov wrote:
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> index a1efa7907a0b..5558a1ec3dc9 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -87,7 +87,7 @@ struct kvm_clock_pairing {
>  #define KVM_MAX_MMU_OP_BATCH           32
>  
>  #define KVM_ASYNC_PF_ENABLED                   (1 << 0)
> -#define KVM_ASYNC_PF_SEND_ALWAYS               (1 << 1)
> +#define KVM_ASYNC_PF_SEND_ALWAYS               (1 << 1) /* deprecated */
>  #define KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT     (1 << 2)
>  #define KVM_ASYNC_PF_DELIVERY_AS_INT           (1 << 3)
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 83fe0a78146f..cd15e738ca9b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3585,7 +3585,6 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
>                                         sizeof(u64)))
>                 return 1;
>  
> -       vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
>         vcpu->arch.apf.delivery_as_pf_vmexit = data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
>  
>         kvm_async_pf_wakeup_all(vcpu);
> @@ -13374,8 +13373,7 @@ static bool kvm_can_deliver_async_pf(struct kvm_vcpu *vcpu)
>         if (!kvm_pv_async_pf_enabled(vcpu))
>                 return false;
>  
> -       if (vcpu->arch.apf.send_user_only &&
> -           kvm_x86_call(get_cpl)(vcpu) == 0)
> +       if (kvm_x86_call(get_cpl)(vcpu) == 0)

By x86's general definition of "user", this should be "!= 3" :-)