On Tue, Jun 19, 2018 at 11:08:46AM +0200, Thomas Gleixner wrote:
> On Fri, 15 Jun 2018, Fenghua Yu wrote:
>
> > +static ssize_t tsc_khz_show(struct device *dev, struct device_attribute
> > *attr,
> > + char *buf)
> > +{
> > + return sprintf(buf, "%d\n", tsc_khz);
> > +}
> > +
> > static DEVICE_ATTR_RW(umwait_disable_c0_2);
> > +static DEVICE_ATTR_RO(tsc_khz);
>
> The right place to expose that information is the VDSO and a helper
> function which allows to convert from nsec to TSC.
Sure. I will do that.
>
> > static struct attribute *umwait_attrs[] = {
> > &dev_attr_umwait_disable_c0_2.attr,
> > @@ -92,6 +100,15 @@ static int __init umwait_init(void)
> > if (ret)
> > return ret;
> >
> > + /* Only add the tsc_khz interface when the value is known. */
>
> Why so? The only reason why you don't want to expose TSC frequency is when
> it's not constant frequency.
> > + if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
>
Thanks.
-Fenghua
