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Date:   Wed, 30 Nov 2022 15:43:56 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     liujing <liujing@cmss.chinamobile.com>
Cc:     pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, dave.hansen@linux.intel.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: Redundant variable assignments can be merged
Message-ID: <Y4d6PEGv4pvKyJeF@google.com>
References: <20221130115504.4282-1-liujing@cmss.chinamobile.com>
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In-Reply-To: <20221130115504.4282-1-liujing@cmss.chinamobile.com>
Precedence: bulk

State what the patch does, not what can be done.  And "redundant" isn't the right
word to describe this.

On Wed, Nov 30, 2022, liujing wrote:
> When reading kvm code, find the 'r' variable declaration
> and then assign the value in kvm_vm_ioctl_get_irqchip and
> kvm_vm_ioctl_set_irqchip function, It can be combined into one sentence.

Why though?  I actually kinda like the existing code.

That said, what about removing the variable entirely?  That'd also avoid the
unnecessary call to kvm_pic_update_irq() in set's error path.

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d2ad383da998..898fce19430a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6011,9 +6011,7 @@ static unsigned long kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
 static int kvm_vm_ioctl_get_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
 {
        struct kvm_pic *pic = kvm->arch.vpic;
-       int r;
 
-       r = 0;
        switch (chip->chip_id) {
        case KVM_IRQCHIP_PIC_MASTER:
                memcpy(&chip->chip.pic, &pic->pics[0],
@@ -6027,18 +6025,15 @@ static int kvm_vm_ioctl_get_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
                kvm_get_ioapic(kvm, &chip->chip.ioapic);
                break;
        default:
-               r = -EINVAL;
-               break;
+               return -EINVAL;
        }
-       return r;
+       return 0;
 }
 
 static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
 {
        struct kvm_pic *pic = kvm->arch.vpic;
-       int r;
 
-       r = 0;
        switch (chip->chip_id) {
        case KVM_IRQCHIP_PIC_MASTER:
                spin_lock(&pic->lock);
@@ -6056,11 +6051,10 @@ static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
                kvm_set_ioapic(kvm, &chip->chip.ioapic);
                break;
        default:
-               r = -EINVAL;
-               break;
+               return -EINVAL;
        }
        kvm_pic_update_irq(pic);
-       return r;
+       return 0;
 }
 
 static int kvm_vm_ioctl_get_pit(struct kvm *kvm, struct kvm_pit_state *ps)