Re: [PATCH] Revert "MIPS: Remove race window in page fault handling"

[Lars Persson]

Ralf

I remember now that we have applied to our tree the proposed patch
titled "MIPS HIGHMEM fixes for cache aliasing and non-DMA I/O".

This patch changes the semantics of flush_dcache_page() by using
page_mapped() instead of mapping_mapped() to decide if the flush should
be lazy. Is it this change that makes us get lazy flushes for code
mappings and therefore exposing the problem ? The ARM port which has
made a similar change to set_pte_at() also uses page_mapped() to decide
if lazy flushing is possible.

If this is true, then upstream might not need my patch. 

- Lars



On ons, 2014-12-03 at 14:42 +0100, Ralf Baechle wrote:
> Lars,
> 
> normally set_pte_at() is invoked in a 
> 
>   cache_flush_*()
>   set_pte_at()
>   tlb_flush_*()
> 
> sequence.  So I'm wondering if you're trying to fix something in set_pte_at
> that actually ought to be fixed in the cache_flush_*() function.
> 
> I'm wondering, have you identified which cache flush function in particular
> was used in the sequence in your particular bug's case?
> 
>   Ralf



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