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Violators will be prosecuted for from ; Thu, 23 Apr 2020 12:00:32 +0100 Subject: Re: [PATCH v2 1/7] KVM: s390: clean up redundant 'kvm_run' parameters References: <20200422125810.34847-1-tianjia.zhang@linux.alibaba.com> <20200422125810.34847-2-tianjia.zhang@linux.alibaba.com> <20200422154543.2efba3dd.cohuck@redhat.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 Date: Thu, 23 Apr 2020 13:00:25 +0200 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-s390-owner@vger.kernel.org List-ID: To: Tianjia Zhang , Cornelia Huck 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 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 wrote: >> >>> On 2020/4/23 0:04, Cornelia Huck wrote: >>>> On Wed, 22 Apr 2020 17:58:04 +0200 >>>> Christian Borntraeger wrote: >>>>    >>>>> On 22.04.20 15:45, Cornelia Huck wrote: >>>>>> On Wed, 22 Apr 2020 20:58:04 +0800 >>>>>> Tianjia Zhang 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 >>>>>>> --- >>>>>>>    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.