[RFC PATCH 1/4] powerpc/64s/radix: Fix memory hotplug section page table creation

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:
> create_physical_mapping expects physical addresses, but creating and
> splitting these mappings after boot is supplying virtual (effective)
> addresses. This can be hit by booting with limited memory then probing
> new physical memory sections.
>
> Cc: Reza Arbab <arbab at linux.vnet.ibm.com>
> Fixes: 6cc27341b21a8 ("powerpc/mm: add radix__create_section_mapping()")
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

This is not catastrophic because create_physical_mapping() just uses
start/end to construct virtual addresses anyway, and __va(__va(x)) == __va(x) ?

Although we do pass those through as region_start/end which then go to
memblock_alloc_try_nid(). But I guess that doesn't happen after boot,
which is the case you're talking about.

So I think looks good, change log could use a bit more detail though :)

cheers

> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index b4ca9e95e678..c5cc16ab1954 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -902,7 +902,7 @@ int __meminit radix__create_section_mapping(unsigned long start, unsigned long e
>  		return -1;
>  	}
>  
> -	return create_physical_mapping(start, end, nid);
> +	return create_physical_mapping(__pa(start), __pa(end), nid);
>  }
>  
>  int __meminit radix__remove_section_mapping(unsigned long start, unsigned long end)
> -- 
> 2.20.1