Re: [RFC 1/5] x86: Clean up cr4 manipulation

[Borislav Petkov]

On Thu, Oct 16, 2014 at 01:18:58PM +0200, Borislav Petkov wrote:
> 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);
> > > +}

Btw, on a related note, we probably should check whether the bits we
want to set/clear are already set/cleared and then save us the CR4
write.

It probably won't be the case all that much but still...

-- 
Regards/Gruss,
    Boris.
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