linux-kernel - Re: [PATCH] arch: x86: kvm: x86.c: Cleaning up uninitialized variables

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Date:	Tue, 03 Jun 2014 14:04:04 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Gleb Natapov <gleb@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch: x86: kvm: x86.c:  Cleaning up uninitialized variables

Il 01/06/2014 01:05, Rickard Strandqvist ha scritto:
> There is a risk that the variable will be used without being initialized.
> 
> This was largely found by using a static code analysis program called cppcheck.
> 
> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>

No, there isn't.  The full context looks like this:

        longmode = is_long_mode(vcpu) && cs_l == 1;
        if (!longmode) {
                param = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDX) << 32) |
                        (kvm_register_read(vcpu, VCPU_REGS_RAX) & 0xffffffff);
                ingpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RBX) << 32) |
                        (kvm_register_read(vcpu, VCPU_REGS_RCX) & 0xffffffff);
                outgpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDI) << 32) |
                        (kvm_register_read(vcpu, VCPU_REGS_RSI) & 0xffffffff);
        }
#ifdef CONFIG_X86_64
        else {
                param = kvm_register_read(vcpu, VCPU_REGS_RCX);
                ingpa = kvm_register_read(vcpu, VCPU_REGS_RDX);
                outgpa = kvm_register_read(vcpu, VCPU_REGS_R8);
        }
#endif

and longmode must be zero if !CONFIG_X86_64:

static inline int is_long_mode(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_X86_64
        return vcpu->arch.efer & EFER_LMA;
#else
        return 0;
#endif
}

So it's the static checker that cannot understand #ifdef well
enough and ought to be fixed.

Paolo
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