lkml.org 
[lkml]   [2020]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH v2 1/3] mm/gup: fix gup_fast with dynamic page table folding
On Wed, Sep 09, 2020 at 07:25:34PM +0200, Gerald Schaefer wrote:
> I actually had to draw myself a picture to get some hold of
> this, or rather a walk-through with a certain pud-crossing
> range in a folded 3-level scenario. Not sure if I would have
> understood my explanation above w/o that, but I hope you can
> make some sense out of it. Or draw yourself a picture :-)

What I don't understand is how does anything work with S390 today?

If the fix is only to change pxx_addr_end() then than generic code
like mm/pagewalk.c will iterate over a *different list* of page table
entries.

It's choice of entries to look at is entirely driven by pxx_addr_end().

Which suggest to me that mm/pagewalk.c also doesn't work properly
today on S390 and this issue is not really about stack variables?

Fundamentally if pXX_offset() and pXX_addr_end() must be consistent
together, if pXX_offset() is folded then pXX_addr_end() must cause a
single iteration of that level.

Jason

\
 
 \ /
  Last update: 2020-09-09 20:06    [W:0.105 / U:0.872 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site