lkml.org 
[lkml]   [2011]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking
On Wed, Sep 07, 2011 at 08:09:37PM +0300, Avi Kivity wrote:
> >But then the downside
> >here is we accidentally handle an NMI that was latched. This would cause
> >a 'Dazed on confused' message as that NMI was already handled by the
> >previous NMI.
> >
> >We are working on an algorithm to detect this condition and flag it
> >(nothing complicated). But it may never be perfect.
> >
> >On the other hand, what else are we going to do with an edge-triggered
> >shared interrupt line?
> >
>
> How about, during NMI, save %rip to a per-cpu variable. Handle just
> one cause. If, on the next NMI, we hit the same %rip, assume
> back-to-back NMI has occured and now handle all causes.

So I got around to implementing this and it seems to work great. The back
to back NMIs are detected properly using the %rip and that info is passed to
the NMI notifier. That info is used to determine if only the first
handler to report 'handled' is executed or _all_ the handlers are
executed.

I think all the 'unknown' NMIs I generated with various perf runs have
disappeared. I'll post a new version of my nmi notifier rewrite soon.

Thanks for the great suggestion Avi!

Cheers,
Don


\
 
 \ /
  Last update: 2011-09-13 20:43    [W:0.120 / U:0.804 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site