linux-kernel - Re: [PATCH] KVM: x86: remove duplicated KVM_REQ

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Message-ID: <87ftfogfqs.fsf@vitty.brq.redhat.com>
Date:   Thu, 06 Feb 2020 11:41:15 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com
Subject: Re: [PATCH] KVM: x86: remove duplicated KVM_REQ_EVENT request

linmiaohe <linmiaohe@...wei.com> writes:

> From: Miaohe Lin <linmiaohe@...wei.com>
>
> The KVM_REQ_EVENT request is already made in kvm_set_rflags(). We should
> not make it again.
>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  arch/x86/kvm/x86.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fbabb2f06273..212282c6fb76 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8942,7 +8942,6 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
>  
>  	kvm_rip_write(vcpu, ctxt->eip);
>  	kvm_set_rflags(vcpu, ctxt->eflags);
> -	kvm_make_request(KVM_REQ_EVENT, vcpu);

I would've actually done it the other way around and removed
kvm_make_request() from kvm_set_rflags() as it is not an obvious
behavior (e.g. why kvm_rip_write() doens't do that and kvm_set_rflags()
does ?) adding kvm_make_request() to all call sites.

In case this looks like too big of a change with no particular gain I'd
suggest you at least leave a comment above kvm_set_rflags(), something
like

"kvm_make_request() also requests KVM_REQ_EVENT"

>  	return 1;
>  }
>  EXPORT_SYMBOL_GPL(kvm_task_switch);

-- 
Vitaly