On Thu, 15 Dec 2016, Andy Lutomirski wrote:
> On Thu, Dec 15, 2016 at 8:44 AM, Thomas Gleixner <t...@linutronix.de> wrote:
> > +static inline void cr4_toggle_bits(unsigned long mask)
> > +{
> > + unsigned long cr4;
> > +
> > + cr4 = this_cpu_read(cpu_tlbstate.cr4);
> > + cr4 ^= mask;
> > + this_cpu_write(cpu_tlbstate.cr4, cr4);
> > + __write_cr4(cr4);
> > +}
>
> This scares me for the same reason as BTF, although this should at
> least be less fragile. But how about:
If that is fragile then all cr4 manipulation code is fragile because it
relies on cpu_tlbstate.cr4. The TIF flag and that per cpu thing are kept in
sync.
Thanks,
tglx
