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Date:   Thu, 07 May 2020 00:59:03 -0700
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Subject: RE: [PATCH] x86: bitops: fix build regression
To:     David Laight <David.Laight@ACULAB.COM>,
        "'Brian Gerst'" <brgerst@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        stable <stable@vger.kernel.org>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        "kernelci . org bot" <bot@kernelci.org>,
        Andy Shevchenko <andriy.shevchenko@intel.com>,
        Ilie Halip <ilie.halip@gmail.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Marco Elver <elver@google.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Daniel Axtens <dja@axtens.net>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "clang-built-linux@googlegroups.com" 
        <clang-built-linux@googlegroups.com>
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On May 7, 2020 12:44:44 AM PDT, David Laight <David=2ELaight@ACULAB=2ECOM> =
wrote:
>From: Brian Gerst
>> Sent: 07 May 2020 07:18
>=2E=2E=2E
>> > --- a/arch/x86/include/asm/bitops=2Eh
>> > +++ b/arch/x86/include/asm/bitops=2Eh
>> > @@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long
>*addr)
>> >         if (__builtin_constant_p(nr)) {
>> >                 asm volatile(LOCK_PREFIX "orb %1,%0"
>> >                         : CONST_MASK_ADDR(nr, addr)
>> > -                       : "iq" (CONST_MASK(nr) & 0xff)
>> > +                       : "iq" ((u8)(CONST_MASK(nr) & 0xff))
>>=20
>> I think a better fix would be to make CONST_MASK() return a u8 value
>> rather than have to cast on every use=2E
>
>Or assign to a local variable - then it doesn't matter how
>the value is actually calculated=2E So:
>			u8 mask =3D CONST_MASK(nr);
>			asm volatile(LOCK_PREFIX "orb %1,%0"
>				: CONST_MASK_ADDR(nr, addr)
>				: "iq" mask
>
>	David
>
>-
>Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes,
>MK1 1PT, UK
>Registration No: 1397386 (Wales)

"const u8" please=2E=2E=2E
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E