On Mon, Jun 23, 2014 at 09:35:00AM +0200, Peter Zijlstra wrote: > On Thu, Jun 19, 2014 at 01:40:41PM -0700, Andi Kleen wrote: > > On Thu, Jun 19, 2014 at 10:31:29PM +0200, Stephane Eranian wrote: > > > On Thu, Jun 19, 2014 at 10:18 PM, Andi Kleen <a...@linux.intel.com> wrote: > > > >> I don't quite understand that. > > > >> You need to know which events support PEBS. You need a table > > > > > > > > We're talking about the kernel allowing things here. > > > > Yes the user still needs to know what supports PEBS, but > > > > that doesn't concern the kernel. > > > > > > > Just need to make sure you don't return bogus information. > > > > GIGO. We only need to prevent security issues. > > > Yes if the user specifies a bogus raw event it will not count. > > That's fine. The important part is just that nothing ever crashes. > > Right. But IIRC you were previously arguing that we can in fact crash > the machine with raw PEBS events, as illustrated with the SNB PEBS > cycles 'event'.
The potential problem could only happen for a recognized PEBS event/umask, but with unsupported flag combinations. That is what the SDM warns about in 18.8.4. If the event is not recognized as PEBS it will just effectively disable the event. > Which is where my strict_pebs patch came from; by default only allow the > sanitized known-safe list of events, but allow the system administrator > to disable that test and allow any PEBS event. I don't think we need to enforce the list of events (except for the few with special limited counters) -Andi -- a...@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
