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Message-ID: <20141016111858.GB25025@nazgul.tnic>
Date:	Thu, 16 Oct 2014 13:18:58 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Erik Bosman <ebn310@....vu.nl>
Subject: Re: [RFC 1/5] x86: Clean up cr4 manipulation

On Thu, Oct 16, 2014 at 10:16:33AM +0200, Peter Zijlstra wrote:
> On Tue, Oct 14, 2014 at 03:57:35PM -0700, Andy Lutomirski wrote:
> > +/* Set in this cpu's CR4. */
> > +static inline void cr4_set(unsigned long mask)
> > +{
> > +	unsigned long cr4;
> > +
> > +	cr4 = read_cr4();
> > +	cr4 |= mask;
> > +	write_cr4(cr4);
> > +}
> > +
> > +/* Clear in this cpu's CR4. */
> > +static inline void cr4_clear(unsigned long mask)
> > +{
> > +	unsigned long cr4;
> > +
> > +	cr4 = read_cr4();
> > +	cr4 &= ~mask;
> > +	write_cr4(cr4);
> > +}
> 
> I would have called these cr4_or() and cr4_nand(). When first reading
> this I expected cr4_set() to be a pure write_cr4() and cr4_clear() to do
> write_cr4(0) -- which obviously doesn't make too much sense.
> 
> 
> cr4_{set,clear}_mask() might maybe be clearer but is more typing, and
> the logical ops as suggested should have unambiguous meaning.

Or maybe ...{set,clear}_bits() because we're setting/clearing a mask of
a bunch of bits...

-- 
Regards/Gruss,
    Boris.
--
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