DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com EE2F25F7AD
Subject: Re: [PATCH] KVM: x86: fix clang build
To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
        Dmitry Vyukov <dvyukov@google.com>
References: <20170913131346.2701-1-rkrcmar@redhat.com>
From: David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <352d4dce-a0d0-67cf-edd3-1d81bf2b3f96@redhat.com>
Date: Wed, 13 Sep 2017 15:15:19 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.3.0
MIME-Version: 1.0
In-Reply-To: <20170913131346.2701-1-rkrcmar@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1230
Lines: 37

On 13.09.2017 15:13, Radim Krčmář wrote:
> Clang resolves __builtin_constant_p() to false even if the expression is
> constant in the end.  The only purpose of that expression was to
> differentiate a case where the following expression couldn't be checked
> at compile-time, so we can just remove the check.
> 
> Clang handles the following two correctly.  Turn it into BUG_ON if there
> are any more problems with this.
> 
> Fixes: d6321d493319 ("KVM: x86: generalize guest_cpuid_has_ helpers")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
>  arch/x86/kvm/cpuid.h | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 1ea3c0e1e3a9..0bc5c1315708 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -59,7 +59,6 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned x86_feature)
>  {
>  	unsigned x86_leaf = x86_feature / 32;
>  
> -	BUILD_BUG_ON(!__builtin_constant_p(x86_leaf));
>  	BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
>  	BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
>  
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

Thanks,

David