[PATCH 1/3] powerpc/book3s64/hash/4k: 4k supports only 16TB linear mapping

[Samuel Holland]

Hello,

On 9/17/19 9:57 AM, Aneesh Kumar K.V wrote:
> With commit: 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in the
> same 0xc range"), we now split the 64TB address range into 4 contexts each of
> 16TB. That implies we can do only 16TB linear mapping. Make sure we don't
> add physical memory above 16TB if that is present in the system.
> 
> Fixes: 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in thesame 0xc range")
> Reported-by: Cameron Berkenpas <cam at neo-zeon.de>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> ---
>  arch/powerpc/include/asm/book3s/64/mmu.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
> index bb3deb76c951..86cce8189240 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu.h
> @@ -35,12 +35,16 @@ extern struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
>   * memory requirements with large number of sections.
>   * 51 bits is the max physical real address on POWER9
>   */
> -#if defined(CONFIG_SPARSEMEM_VMEMMAP) && defined(CONFIG_SPARSEMEM_EXTREME) &&  \
> -	defined(CONFIG_PPC_64K_PAGES)
> +
> +#if defined(CONFIG_PPC_64K_PAGES)
> +#if defined(CONFIG_SPARSEMEM_VMEMMAP) && defined(CONFIG_SPARSEMEM_EXTREME)

This prevents accessing physical memory over 16TB with 4k pages and radix MMU as
well. Was this intentional?

>  #define MAX_PHYSMEM_BITS 51
>  #else
>  #define MAX_PHYSMEM_BITS 46
>  #endif
> +#else /* CONFIG_PPC_64K_PAGES */
> +#define MAX_PHYSMEM_BITS 44
> +#endif
>  
>  /* 64-bit classic hash table MMU */
>  #include <asm/book3s/64/mmu-hash.h>
> 
Cheers,
Samuel