Re: Hardware Error Kernel Mini-Summit

[Ingo Molnar <mingo@elte.hu>]

* Tony Luck <tony.luck@intel.com> wrote:

> > This gives us a broad platform to add various RAS 
> > events as well, beyond raw hardware events: we could 
> > for example events for various system anomalies such 
> > as lockup messages, kernel warnings/oopses, IOMMU 
> > exceptions - maybe even pure software concepts such as 
> > fatal segmentation fault events, etc. etc.
> 
> This looks like sticky ground.  I can see the event 
> mechanism passing data to a user daemon working well for 
> all kinds of corrected and minor errors. But when you 
> start talking about lockups and fatal errors things get 
> a lot trickier. Often the main concern at this point is 
> error containment. Making sure that the flaky data 
> doesn't become visible (saved to storage, transmitted to 
> the network, etc.). [...]

I was pointing beyond the narrow hardware (memory) error 
point of view, towards a more generic 'system health' 
thinking.

In the broader view it may makes sense to for example 
define policy over excessive number of segfaults on a 
server system (where excessive segfaults are an anomaly), 
or a suspiciously large number of soft IO errors, etc.

But yes, of course, when it comes to hard memory errors, 
those take precedence, and handling them (and 
saving/propagating information about them while we still 
can) is a priority.

> [...] Getting from a machine check handler through some 
> context switches (and page faults etc.) to a user level 
> daemon before the error gets recorded looks to be really 
> hard.

As Boris mentioned it too, critical policy action can and 
will be done straight in the kernel.

	Ingo