Re: [patch V6 10/14] MDS basics 10

On Wed, 6 Mar 2019, speck for Borislav Petkov wrote:
> On Fri, Mar 01, 2019 at 10:47:48PM +0100, speck for Thomas Gleixner wrote:
> > +/* Update the static key controlling the MDS CPU buffer clear in idle */
> > +static void update_mds_branch_idle(void)
> > +{
> > +	/*
> > +	 * Enable the idle clearing on CPUs which are affected only by
> > +	 * MDBDS and not any other MDS variant. The other variants cannot
> > +	 * be mitigated when SMT is enabled,
> 
> ... but we're not enabling the key when SMT on those is disabled,
> AFAICT. Or is that coming later?

Five lines down ....
 
> > so clearing the buffers on
> > +	 * idle would be a window dressing exercise.
> > +	 */
> > +	if (!boot_cpu_has(X86_BUG_MSBDS_ONLY))
> 
> 	if (!boot_cpu_has_bug

Fixed.

> > +		return;
> > +
> > +	if (sched_smt_active())


... here is the decision whether to enable or disable.

> > +		static_branch_enable(&mds_idle_clear);
> > +	else
> > +		static_branch_disable(&mds_idle_clear);
> > +}

Thanks,

	tglx