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References: <20211018183608.589083-1-pbonzini@redhat.com>
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From:   Jim Mattson <jmattson@google.com>
Date:   Mon, 18 Oct 2021 11:41:26 -0700
Message-ID: <CALMp9eSm4ko=D_3fnHiUiWTC+bc9dJQUpXb+s5BDwPsM+vST4w@mail.gmail.com>
Subject: Re: [PATCH v2] KVM: x86: avoid warning with -Wbitwise-instead-of-logical
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        torvic9@mailbox.org
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On Mon, Oct 18, 2021 at 11:36 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> This is a new warning in clang top-of-tree (will be clang 14):
>
> In file included from arch/x86/kvm/mmu/mmu.c:27:
> arch/x86/kvm/mmu/spte.h:318:9: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
>         return __is_bad_mt_xwr(rsvd_check, spte) |
>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                                                  ||
> arch/x86/kvm/mmu/spte.h:318:9: note: cast one or both operands to int to silence this warning
>
> The code is fine, but change it anyway to shut up this clever clogs
> of a compiler.
>
> Reported-by: torvic9@mailbox.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/x86/kvm/mmu/spte.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 7c0b09461349..66782e796c0a 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -315,7 +315,7 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
>          * bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc
>          * (this is extremely unlikely to be short-circuited as true).
>          */
> -       return __is_bad_mt_xwr(rsvd_check, spte) |
> +       return __is_bad_mt_xwr(rsvd_check, spte) ||
>                __is_rsvd_bits_set(rsvd_check, spte, level);
>  }
You should probably elide the comment above.

Reviewed-by: Jim Mattson <jmattson@google.com>