Re: [PATCH v3 7/8] powerpc/mm: Consolidate radix and hash address map details

[Nicholas Piggin <npiggin@gmail.com>]

Aneesh Kumar K.V's on April 16, 2019 8:07 pm:
> We now have
> 
> 4K page size config
> 
>  kernel_region_map_size = 16TB
>  kernel vmalloc start   = 0xc000100000000000
>  kernel IO start        = 0xc000200000000000
>  kernel vmemmap start   = 0xc000300000000000
> 
> with 64K page size config:
> 
>  kernel_region_map_size = 512TB
>  kernel vmalloc start   = 0xc008000000000000
>  kernel IO start        = 0xc00a000000000000
>  kernel vmemmap start   = 0xc00c000000000000

Hey Aneesh,

I like the series, I like consolidating the address spaces into 0xc,
and making the layouts match or similar isn't a bad thing. I don't
see any real reason to force limitations on one layout or another --
you could make the argument that 4k radix should match 64k radix
as much as matching 4k hash IMO.

I wouldn't like to tie them too strongly to the same base defines
that force them to stay in sync.

Can we drop this patch? Or at least keep the users of the H_ and R_
defines and set them to the same thing in map.h?


> diff --git a/arch/powerpc/include/asm/book3s/64/map.h b/arch/powerpc/include/asm/book3s/64/map.h
> new file mode 100644
> index 000000000000..5c01f8c18d61
> --- /dev/null
> +++ b/arch/powerpc/include/asm/book3s/64/map.h
> @@ -0,0 +1,80 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_BOOK3S_64_MAP_H_
> +#define _ASM_POWERPC_BOOK3S_64_MAP_H_
> +
> +/*
> + * We use MAX_EA_BITS_PER_CONTEXT (hash specific) here just to make sure we pick
> + * the same value for hash and radix.
> + */
> +#ifdef CONFIG_PPC_64K_PAGES
> +
> +/*
> + * Each context is 512TB size. SLB miss for first context/default context
> + * is handled in the hotpath.

Now everything is handled in the slowpath :P I guess that's a copy
paste of the comment which my SLB miss patch should have fixed it.

Thanks,
Nick