linux-kernel - Re: [PATCH] kvm/x86 : avoid shifting signed 32-bit value by 31 bits

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Date:   Mon, 15 Oct 2018 10:30:43 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, peng.hao2@....com.cn,
        richard.weiyang@...il.com
Cc:     penghao122@...a.com.cn, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, joro@...tes.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] kvm/x86 : avoid shifting signed 32-bit value by 31 bits

On 10/15/18 10:23 AM, Paolo Bonzini wrote:
> 
> Even for a value from a 32-bit register?  That would be _BIT, which
> doesn't exist.
> 

Just use _BITUL(). gcc is smart enough to know that that the resulting value
is representable in 32 bits.

Or if you really care, submit a patch to create _BITU(), but I don't
personally see much of a point.

	-hpa