Re: [PATCH v2] mm: Track page table modifications in __apply_to_page_range()

[Chris Wilson]

Quoting Andrew Morton (2020-08-21 23:34:12)
> On Fri, 21 Aug 2020 14:37:46 +0200 Joerg Roedel <joro@xxxxxxxxxx> wrote:
> 
> > The __apply_to_page_range() function is also used to change and/or
> > allocate page-table pages in the vmalloc area of the address space.
> > Make sure these changes get synchronized to other page-tables in the
> > system by calling arch_sync_kernel_mappings() when necessary.
> > 
> > Tested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> #x86-32
> > Cc: <stable@xxxxxxxxxxxxxxx> # v5.8+
> 
> I'm trying to figure out how you figured out that this is 5.8+.  Has a
> particular misbehaving commit been identified?

The two commits of relevance, in my eyes, were

  2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified")
  86cf69f1d893 ("x86/mm/32: implement arch_sync_kernel_mappings()")

I can reproduce the failure on v5.8, but not on v5.7. A bisect would
seem to be plausible.
-Chris