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Subject: Re: [PATCH v2 1/7] KVM: s390: clean up redundant 'kvm_run' parameters
To:     Cornelia Huck <cohuck@redhat.com>
Cc:     Christian Borntraeger <borntraeger@de.ibm.com>,
        pbonzini@redhat.com, tsbogend@alpha.franken.de, paulus@ozlabs.org,
        mpe@ellerman.id.au, benh@kernel.crashing.org,
        frankja@linux.ibm.com, david@redhat.com, heiko.carstens@de.ibm.com,
        gor@linux.ibm.com, sean.j.christopherson@intel.com,
        vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
        joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, x86@kernel.org, hpa@zytor.com, maz@kernel.org,
        james.morse@arm.com, julien.thierry.kdev@gmail.com,
        suzuki.poulose@arm.com, christoffer.dall@arm.com,
        peterx@redhat.com, thuth@redhat.com, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200422125810.34847-1-tianjia.zhang@linux.alibaba.com>
 <20200422125810.34847-2-tianjia.zhang@linux.alibaba.com>
 <20200422154543.2efba3dd.cohuck@redhat.com>
 <dc5e0fa3-558b-d606-bda9-ed281cf9e9ae@de.ibm.com>
 <20200422180403.03f60b0c.cohuck@redhat.com>
 <5e1e126d-f1b0-196c-594b-4289d0afb9a8@linux.alibaba.com>
 <20200423123901.72a4c6a4.cohuck@redhat.com>
From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Message-ID: <71344f73-c34f-a373-49d1-5d839c6be5f6@linux.alibaba.com>
Date:   Thu, 23 Apr 2020 18:58:52 +0800
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On 2020/4/23 18:39, Cornelia Huck wrote:
> On Thu, 23 Apr 2020 11:01:43 +0800
> Tianjia Zhang <tianjia.zhang@linux.alibaba.com> wrote:
> 
>> On 2020/4/23 0:04, Cornelia Huck wrote:
>>> On Wed, 22 Apr 2020 17:58:04 +0200
>>> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>>>    
>>>> On 22.04.20 15:45, Cornelia Huck wrote:
>>>>> On Wed, 22 Apr 2020 20:58:04 +0800
>>>>> Tianjia Zhang <tianjia.zhang@linux.alibaba.com> wrote:
>>>>>       
>>>>>> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
>>>>>> structure. Earlier than historical reasons, many kvm-related function
>>>>>
>>>>> s/Earlier than/For/ ?
>>>>>       
>>>>>> parameters retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time.
>>>>>> This patch does a unified cleanup of these remaining redundant parameters.
>>>>>>
>>>>>> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
>>>>>> ---
>>>>>>    arch/s390/kvm/kvm-s390.c | 37 ++++++++++++++++++++++---------------
>>>>>>    1 file changed, 22 insertions(+), 15 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>>>>> index e335a7e5ead7..d7bb2e7a07ff 100644
>>>>>> --- a/arch/s390/kvm/kvm-s390.c
>>>>>> +++ b/arch/s390/kvm/kvm-s390.c
>>>>>> @@ -4176,8 +4176,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>>>>>>    	return rc;
>>>>>>    }
>>>>>>    
>>>>>> -static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>>>>> +static void sync_regs_fmt2(struct kvm_vcpu *vcpu)
>>>>>>    {
>>>>>> +	struct kvm_run *kvm_run = vcpu->run;
>>>>>>    	struct runtime_instr_cb *riccb;
>>>>>>    	struct gs_cb *gscb;
>>>>>>    
>>>>>> @@ -4235,7 +4236,7 @@ static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>>>>>    		}
>>>>>>    		if (vcpu->arch.gs_enabled) {
>>>>>>    			current->thread.gs_cb = (struct gs_cb *)
>>>>>> -						&vcpu->run->s.regs.gscb;
>>>>>> +						&kvm_run->s.regs.gscb;
>>>>>
>>>>> Not sure if these changes (vcpu->run-> => kvm_run->) are really worth
>>>>> it. (It seems they amount to at least as much as the changes advertised
>>>>> in the patch description.)
>>>>>
>>>>> Other opinions?
>>>>
>>>> Agreed. It feels kind of random. Maybe just do the first line (move kvm_run from the
>>>> function parameter list into the variable declaration)? Not sure if this is better.
>>>>   
>>>
>>> There's more in this patch that I cut... but I think just moving
>>> kvm_run from the parameter list would be much less disruptive.
>>>    
>>
>> I think there are two kinds of code(`vcpu->run->` and `kvm_run->`), but
>> there will be more disruptive, not less.
> 
> I just fail to see the benefit; sure, kvm_run-> is convenient, but the
> current code is just fine, and any rework should be balanced against
> the cost (e.g. cluttering git annotate).
> 

cluttering git annotate ? Does it mean Fix xxxx ("comment"). Is it 
possible to solve this problem by splitting this patch?