* Pavel Machek <pa...@ucw.cz> wrote:
> +static void rh_overflow(struct perf_event *event, struct perf_sample_data
> *data, struct pt_regs *regs)
> +{
> + u64 *ts = this_cpu_ptr(&rh_timestamp); /* this is NMI context */
> + u64 now = ktime_get_mono_fast_ns();
> + s64 delta = now - *ts;
> +
> + *ts = now;
> +
> + /* FIXME msec per usec, reverse logic? */
> + if (delta < 64 * NSEC_PER_MSEC)
> + mdelay(56);
> +}
I'd suggest making the absolute delay sysctl tunable, because 'wait 56 msecs'
is
very magic, and do we know it 100% that 56 msecs is what is needed everywhere?
Plus I'd also suggest exposing an 'NMI rowhammer delay count' in
/proc/interrupts,
to make it easier to debug this. (Perhaps only show the line if the count is
nonzero.)
Finally, could we please also add a sysctl and Kconfig that allows this feature
to
be turned on/off, with the default bootup value determined by the Kconfig value
(i.e. by the distribution)? Similar to CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE.
Thanks,
Ingo
