linux-kernel - Re: [PATCH] KVM: x86/mmu: Fix a benign Bitwise vs. Logical OR mixup

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Message-ID: <41a2328e-a64a-0131-920e-06328305919d@redhat.com>
Date:   Wed, 15 Jan 2020 19:20:22 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Arvind Sankar <nivedita@...m.mit.edu>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86/mmu: Fix a benign Bitwise vs. Logical OR mixup

On 09/01/20 17:36, Sean Christopherson wrote:
>>> You also don't want to convert the expression result to zero.
>> The function is static inline bool, so it's almost certainly a mistake
>> originally. The != 0 is superfluous, but this will get inlined anyway.
> Ya, the bitwise-OR was added in commit 25d92081ae2f ("nEPT: Add nEPT
> violation/misconfigration support"), and AFAICT it's unintentional.

It may not be intentional in this case, but it's certainly the kind of
code that I would have fun writing. :)

Paolo