linux-kernel - Re: [PATCH] KVM: x86: eliminate some unreachable code

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Date:   Mon, 17 Feb 2020 17:16:34 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com
Subject: Re: [PATCH] KVM: x86: eliminate some unreachable code

linmiaohe <linmiaohe@...wei.com> writes:

> From: Miaohe Lin <linmiaohe@...wei.com>
>
> These code are unreachable, remove them.
>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 1 -
>  arch/x86/kvm/x86.c     | 3 ---
>  2 files changed, 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index bb5c33440af8..b6d4eafe01cf 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -4505,7 +4505,6 @@ static bool rmode_exception(struct kvm_vcpu *vcpu, int vec)
>  	case GP_VECTOR:
>  	case MF_VECTOR:
>  		return true;
> -	break;
>  	}
>  	return false;
>  }

Unrelated to your change but what I don't in rmode_exception() is the
second "/* fall through */" instead of just 'return true;', it makes it
harder to read.

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fbabb2f06273..a597009aefd7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3081,7 +3081,6 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		break;
>  	case APIC_BASE_MSR ... APIC_BASE_MSR + 0x3ff:
>  		return kvm_x2apic_msr_read(vcpu, msr_info->index, &msr_info->data);
> -		break;
>  	case MSR_IA32_TSCDEADLINE:
>  		msr_info->data = kvm_get_lapic_tscdeadline_msr(vcpu);
>  		break;
> @@ -3164,7 +3163,6 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		return kvm_hv_get_msr_common(vcpu,
>  					     msr_info->index, &msr_info->data,
>  					     msr_info->host_initiated);
> -		break;
>  	case MSR_IA32_BBL_CR_CTL3:
>  		/* This legacy MSR exists but isn't fully documented in current
>  		 * silicon.  It is however accessed by winxp in very narrow
> @@ -8471,7 +8469,6 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
>  		break;
>  	default:
>  		return -EINTR;
> -		break;
>  	}
>  	return 1;
>  }

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly