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SubjectRe: [RFC PATCH 1/2] KVM: x86: Add a framework for supporting MSR-based features
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On 14/02/2018 17:44, Borislav Petkov wrote:
> 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.
>

Nice point---even better, just push srcu_read_lock/unlock to msr_io or
even msr_io's callers.

Thanks,

Paolo

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