Re: pipe/page fault oddness.

From: Dave Jones
Date: Tue Sep 30 2014 - 12:07:50 EST

On Tue, Sep 30, 2014 at 12:03:06PM -0400, Rik van Riel wrote:

> > What kind of CPU is the problematic machine? There was some
> > question about just how architectural the whole "TLB entry causing
> > a page fault gets invalidated automatically" really is.
> Intel people told me at the time that the guarantee was architectural.
> I don't know whether other x86 manufacturers know this...
> Doing a local tlb flush from ptep_set_access_flags seems appropriate,
> if that is indeed the issue.
> On the other hand, do_wp_page does not seem to do a tlb flush when
> the old page is reused, so CPUs do get rid of inappropriate TLB
> entries. We would have noticed do_wp_page not working right :)

The puzzling thing is we've had that code change for two years
without issue. This isn't a new machine, so why would it only
be showing up bad effects now ?


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