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

[Andy Lutomirski]

On Thu, Oct 16, 2014 at 4:29 AM, Borislav Petkov <bp@xxxxxxxxx> wrote:
> 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...

That's in patch 2.  I can move it here, though.

>
> --
> Regards/Gruss,
>     Boris.
> --



-- 
Andy Lutomirski
AMA Capital Management, LLC
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