linux-kernel - Re: [PATCH] KVM: x86: fix cocci warnings

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Message-ID: <ce66f713-3d5f-cf3f-8813-d25ee1d2cec7@redhat.com>
Date:   Tue, 16 Nov 2021 08:38:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Vihas Mak <makvihas@...il.com>, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: fix cocci warnings

On 11/15/21 21:49, Peter Zijlstra wrote:
> On Mon, Nov 15, 2021 at 06:06:08PM +0100, Paolo Bonzini wrote:
>> On 11/15/21 12:43, Peter Zijlstra wrote:
>>> On Sun, Nov 14, 2021 at 10:13:12PM +0530, Vihas Mak wrote:
>>>> change 0 to false and 1 to true to fix following cocci warnings:
>>>>
>>>>           arch/x86/kvm/mmu/mmu.c:1485:9-10: WARNING: return of 0/1 in function 'kvm_set_pte_rmapp' with return type bool
>>>>           arch/x86/kvm/mmu/mmu.c:1636:10-11: WARNING: return of 0/1 in function 'kvm_test_age_rmapp' with return type bool
>>>
>>> That script should be deleted, it's absolute garbage.
>>
>> Only a Sith deals in absolutes.
> 
> Is that a star-wars thingy?

Yes, it is.  "If you're not with me, then you're my enemy!" "Only a Sith 
deals in absolutes". :)

> In C 0 is a valid way to spell false, equally, any non-0 value is a
> valid way to spell true. Why would this rate a warn?

Because often 0 means success (if -errno means failure).  So if you 
write false/true consistently for bool and 0 only for int, it's one less 
thing that one can get wrong.  At least that's the rationale.

Paolo

> In fact, when casting _Bool to integer, you get 0 and 1. When looking at
> the memory content of the _Bool variable, you'll get 0 and 1. But we're
> not allowed to write 0 and 1?
>