Re: Getting interrupt every million cache misses

[Peter Zijlstra]

On Thu, Oct 27, 2016 at 10:46:38AM +0200, Pavel Machek wrote:

> And actually, printk() is not needed, udelay(50msec) is. Reason is,
> that DRAM becomes unreliable if about milion cache misses happen in
> under 64msec -- so I'd like to slow the system down in such cases to
> prevent bug from biting me.
> 
> (Details are here
> https://googleprojectzero.blogspot.cz/2015/03/exploiting-dram-rowhammer-bug-to-gain.html
> ). Bug is exploitable to get local root; it is also exploitable to
> gain local code execution from javascript... so it is rather severe.

Cute, a rowhammer defence.

So we can do in-kernel perf events too, see for example
kernel/watchdog.c:wd_hw_attr and its users.

I suppose you want PERF_COUNT_HW_CACHE_MISSES as config, although
depending on platform you could use better (u-arch specific) events.