Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 1/7] KVM: s390: clean up redundant 'kvm_run' parameters
To:     Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        Cornelia Huck <cohuck@redhat.com>
Cc:     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>
 <71344f73-c34f-a373-49d1-5d839c6be5f6@linux.alibaba.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Autocrypt: addr=borntraeger@de.ibm.com; prefer-encrypt=mutual; keydata=
 xsFNBE6cPPgBEAC2VpALY0UJjGmgAmavkL/iAdqul2/F9ONz42K6NrwmT+SI9CylKHIX+fdf
 J34pLNJDmDVEdeb+brtpwC9JEZOLVE0nb+SR83CsAINJYKG3V1b3Kfs0hydseYKsBYqJTN2j
 CmUXDYq9J7uOyQQ7TNVoQejmpp5ifR4EzwIFfmYDekxRVZDJygD0wL/EzUr8Je3/j548NLyL
 4Uhv6CIPf3TY3/aLVKXdxz/ntbLgMcfZsDoHgDk3lY3r1iwbWwEM2+eYRdSZaR4VD+JRD7p8
 0FBadNwWnBce1fmQp3EklodGi5y7TNZ/CKdJ+jRPAAnw7SINhSd7PhJMruDAJaUlbYaIm23A
 +82g+IGe4z9tRGQ9TAflezVMhT5J3ccu6cpIjjvwDlbxucSmtVi5VtPAMTLmfjYp7VY2Tgr+
 T92v7+V96jAfE3Zy2nq52e8RDdUo/F6faxcumdl+aLhhKLXgrozpoe2nL0Nyc2uqFjkjwXXI
 OBQiaqGeWtxeKJP+O8MIpjyGuHUGzvjNx5S/592TQO3phpT5IFWfMgbu4OreZ9yekDhf7Cvn
 /fkYsiLDz9W6Clihd/xlpm79+jlhm4E3xBPiQOPCZowmHjx57mXVAypOP2Eu+i2nyQrkapaY
 IdisDQfWPdNeHNOiPnPS3+GhVlPcqSJAIWnuO7Ofw1ZVOyg/jwARAQABzUNDaHJpc3RpYW4g
 Qm9ybnRyYWVnZXIgKDJuZCBJQk0gYWRkcmVzcykgPGJvcm50cmFlZ2VyQGxpbnV4LmlibS5j
 b20+wsF5BBMBAgAjBQJdP/hMAhsDBwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQEXu8
 gLWmHHy/pA/+JHjpEnd01A0CCyfVnb5fmcOlQ0LdmoKWLWPvU840q65HycCBFTt6V62cDljB
 kXFFxMNA4y/2wqU0H5/CiL963y3gWIiJsZa4ent+KrHl5GK1nIgbbesfJyA7JqlB0w/E/SuY
 NRQwIWOo/uEvOgXnk/7+rtvBzNaPGoGiiV1LZzeaxBVWrqLtmdi1iulW/0X/AlQPuF9dD1Px
 hx+0mPjZ8ClLpdSp5d0yfpwgHtM1B7KMuQPQZGFKMXXTUd3ceBUGGczsgIMipZWJukqMJiJj
 QIMH0IN7XYErEnhf0GCxJ3xAn/J7iFpPFv8sFZTvukntJXSUssONnwiKuld6ttUaFhSuSoQg
 OFYR5v7pOfinM0FcScPKTkrRsB5iUvpdthLq5qgwdQjmyINt3cb+5aSvBX2nNN135oGOtlb5
 tf4dh00kUR8XFHRrFxXx4Dbaw4PKgV3QLIHKEENlqnthH5t0tahDygQPnSucuXbVQEcDZaL9
 WgJqlRAAj0pG8M6JNU5+2ftTFXoTcoIUbb0KTOibaO9zHVeGegwAvPLLNlKHiHXcgLX1tkjC
 DrvE2Z0e2/4q7wgZgn1kbvz7ZHQZB76OM2mjkFu7QNHlRJ2VXJA8tMXyTgBX6kq1cYMmd/Hl
 OhFrAU3QO1SjCsXA2CDk9MM1471mYB3CTXQuKzXckJnxHkHOwU0ETpw8+AEQAJjyNXvMQdJN
 t07BIPDtbAQk15FfB0hKuyZVs+0lsjPKBZCamAAexNRk11eVGXK/YrqwjChkk60rt3q5i42u
 PpNMO9aS8cLPOfVft89Y654Qd3Rs1WRFIQq9xLjdLfHh0i0jMq5Ty+aiddSXpZ7oU6E+ud+X
 Czs3k5RAnOdW6eV3+v10sUjEGiFNZwzN9Udd6PfKET0J70qjnpY3NuWn5Sp1ZEn6lkq2Zm+G
 9G3FlBRVClT30OWeiRHCYB6e6j1x1u/rSU4JiNYjPwSJA8EPKnt1s/Eeq37qXXvk+9DYiHdT
 PcOa3aNCSbIygD3jyjkg6EV9ZLHibE2R/PMMid9FrqhKh/cwcYn9FrT0FE48/2IBW5mfDpAd
 YvpawQlRz3XJr2rYZJwMUm1y+49+1ZmDclaF3s9dcz2JvuywNq78z/VsUfGz4Sbxy4ShpNpG
 REojRcz/xOK+FqNuBk+HoWKw6OxgRzfNleDvScVmbY6cQQZfGx/T7xlgZjl5Mu/2z+ofeoxb
 vWWM1YCJAT91GFvj29Wvm8OAPN/+SJj8LQazd9uGzVMTz6lFjVtH7YkeW/NZrP6znAwv5P1a
 DdQfiB5F63AX++NlTiyA+GD/ggfRl68LheSskOcxDwgI5TqmaKtX1/8RkrLpnzO3evzkfJb1
 D5qh3wM1t7PZ+JWTluSX8W25ABEBAAHCwV8EGAECAAkFAk6cPPgCGwwACgkQEXu8gLWmHHz8
 2w//VjRlX+tKF3szc0lQi4X0t+pf88uIsvR/a1GRZpppQbn1jgE44hgF559K6/yYemcvTR7r
 6Xt7cjWGS4wfaR0+pkWV+2dbw8Xi4DI07/fN00NoVEpYUUnOnupBgychtVpxkGqsplJZQpng
 v6fauZtyEcUK3dLJH3TdVQDLbUcL4qZpzHbsuUnTWsmNmG4Vi0NsEt1xyd/Wuw+0kM/oFEH1
 4BN6X9xZcG8GYUbVUd8+bmio8ao8m0tzo4pseDZFo4ncDmlFWU6hHnAVfkAs4tqA6/fl7RLN
 JuWBiOL/mP5B6HDQT9JsnaRdzqF73FnU2+WrZPjinHPLeE74istVgjbowvsgUqtzjPIG5pOj
 cAsKoR0M1womzJVRfYauWhYiW/KeECklci4TPBDNx7YhahSUlexfoftltJA8swRshNA/M90/
 i9zDo9ySSZHwsGxG06ZOH5/MzG6HpLja7g8NTgA0TD5YaFm/oOnsQVsf2DeAGPS2xNirmknD
 jaqYefx7yQ7FJXXETd2uVURiDeNEFhVZWb5CiBJM5c6qQMhmkS4VyT7/+raaEGgkEKEgHOWf
 ZDP8BHfXtszHqI3Fo1F4IKFo/AP8GOFFxMRgbvlAs8z/+rEEaQYjxYJqj08raw6P4LFBqozr
 nS4h0HDFPrrp1C2EMVYIQrMokWvlFZbCpsdYbBI=
Date:   Thu, 23 Apr 2020 13:00:25 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <71344f73-c34f-a373-49d1-5d839c6be5f6@linux.alibaba.com>
Content-Type: text/plain; charset=UTF-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Message-Id: <1d73b700-4a20-3d7a-66d1-29b5afa03f4d@de.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 23.04.20 12:58, Tianjia Zhang wrote:
> 
> 
> 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?

No its about breaking git blame (and bugfix backports) for just a cosmetic improvement.
And I agree with Conny: the cost is higher than the benefit.