linux-kernel - Re: [RFC PATCH 1/2] KVM: x86: Add a framework for supporting MSR-based features

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Message-ID: <20180214164438.GI18349@pd.tnic>
Date:   Wed, 14 Feb 2018 17:44:39 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [RFC PATCH 1/2] KVM: x86: Add a framework for supporting
 MSR-based features

On Thu, Feb 08, 2018 at 04:58:46PM -0600, Tom Lendacky wrote:
> @@ -2681,11 +2731,15 @@ static int __msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs *msrs,
>  {
>  	int i, idx;
>  
> -	idx = srcu_read_lock(&vcpu->kvm->srcu);
> +	if (vcpu)
> +		idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
>  	for (i = 0; i < msrs->nmsrs; ++i)
>  		if (do_msr(vcpu, entries[i].index, &entries[i].data))
>  			break;
> -	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> +
> +	if (vcpu)
> +		srcu_read_unlock(&vcpu->kvm->srcu, idx);


./include/linux/srcu.h:175:2: warning: ‘idx’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  __srcu_read_unlock(sp, idx);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/kvm/x86.c:2739:9: note: ‘idx’ was declared here
  int i, idx;
         ^~~

I know, silly gcc.

-- 
Regards/Gruss,
    Boris.

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