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

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Message-ID: <a95c89cdcdca4749a1ca4d779ebd4a0a@huawei.com>
Date:   Fri, 7 Feb 2020 02:48:14 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH] KVM: x86: remove duplicated KVM_REQ_EVENT request

Hi：
Vitaly Kuznetsov <vkuznets@...hat.com> writes:
> 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.
>>  	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"

I think adding kvm_make_request() to all call sites is too big without particular gain. And also leave a comment above
kvm_set_rflags() maybe isn't needed as rflags updates is an site that can trigger event injection. Please see commit
(3842d135ff24 KVM: Check for pending events before attempting injection) for detail.

What do you think? Thanks for your review anyway. :)