David Gibson <da...@gibson.dropbear.id.au> writes:
> htab_get_table_size() either retrieve the size of the hash page table (HPT)
> from the device tree - if the HPT size is determined by firmware - or
> uses a heuristic to determine a good size based on RAM size if the kernel
> is responsible for allocating the HPT.
>
> To support a PAPR extension allowing resizing of the HPT, we're going to
> want the memory size -> HPT size logic elsewhere, so split it out into a
> helper function.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> arch/powerpc/include/asm/mmu-hash64.h | 3 +++
> arch/powerpc/mm/hash_utils_64.c | 32 +++++++++++++++++++-------------
> 2 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mmu-hash64.h
> b/arch/powerpc/include/asm/mmu-hash64.h
> index 7352d3f..cf070fd 100644
> --- a/arch/powerpc/include/asm/mmu-hash64.h
> +++ b/arch/powerpc/include/asm/mmu-hash64.h
> @@ -607,6 +607,9 @@ static inline unsigned long get_kernel_vsid(unsigned long
> ea, int ssize)
> context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1;
> return get_vsid(context, ea, ssize);
> }
> +
> +unsigned htab_shift_for_mem_size(unsigned long mem_size);
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_POWERPC_MMU_HASH64_H_ */
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index fdcf9d1..da5d279 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -611,10 +611,26 @@ static int __init htab_dt_scan_pftsize(unsigned long
> node,
> return 0;
> }
>
> -static unsigned long __init htab_get_table_size(void)
> +unsigned htab_shift_for_mem_size(unsigned long mem_size)
> {
> - unsigned long mem_size, rnd_mem_size, pteg_count, psize;
> + unsigned memshift = __ilog2(mem_size);
> + unsigned pshift = mmu_psize_defs[mmu_virtual_psize].shift;
> + unsigned pteg_shift;
> +
> + /* round mem_size up to next power of 2 */
> + if ((1UL << memshift) < mem_size)
> + memshift += 1;
> +
> + /* aim for 2 pages / pteg */
> + pteg_shift = memshift - (pshift + 1);
> +
> + /* 2^11 PTEGS / 2^18 bytes is the minimum htab size permitted
> + * by the architecture */
> + return max(pteg_shift + 7, 18U);
> +}
>
> +static unsigned long __init htab_get_table_size(void)
> +{
> /* If hash size isn't already provided by the platform, we try to
> * retrieve it from the device-tree. If it's not there neither, we
> * calculate it now based on the total RAM size
> @@ -624,17 +640,7 @@ static unsigned long __init htab_get_table_size(void)
> if (ppc64_pft_size)
> return 1UL << ppc64_pft_size;
>
> - /* round mem_size up to next power of 2 */
> - mem_size = memblock_phys_mem_size();
> - rnd_mem_size = 1UL << __ilog2(mem_size);
> - if (rnd_mem_size < mem_size)
> - rnd_mem_size <<= 1;
> -
> - /* # pages / 2 */
> - psize = mmu_psize_defs[mmu_virtual_psize].shift;
> - pteg_count = max(rnd_mem_size >> (psize + 1), 1UL << 11);
> -
> - return pteg_count << 7;
> + return 1UL << htab_shift_for_mem_size(memblock_phys_mem_size());
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> --
> 2.5.0
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