Re: [PATCH v8 2/4] mm: Introduce memblock_isolate_memory

Mike Rapoport
2023-03-16T20:13:22Z

Hi Alexandre,

On Thu, Mar 16, 2023 at 02:17:09PM +0100, Alexandre Ghiti wrote:
> This function allows to split a region in memblock.memory and will be
> useful when setting up the linear mapping with STRICT_KERNEL_RWX: it
> allows to isolate the kernel text/rodata and then avoid to map those
> regions with a PUD/P4D/PGD.

Sorry I've missed it last time. The changelog is fine in the context of
this series, but if you look at it as a part of memblock changelog it
doesn't provide enough background on why memblock_isolate_memory() is
useful.

Can you please add more context so it would be self explanatory?

> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> Reviewed-by: Anup Patel <anup@brainfault.org>
> Tested-by: Anup Patel <anup@brainfault.org>
> ---
> include/linux/memblock.h | 1 +
> mm/memblock.c | 20 ++++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 50ad19662a32..2f7ef97c0da7 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -125,6 +125,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
> +int memblock_isolate_memory(phys_addr_t base, phys_addr_t size);
>
> void memblock_free_all(void);
> void memblock_free(void *ptr, size_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 25fd0626a9e7..e8c651a37012 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -805,6 +805,26 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> return 0;
> }
>
> +/**
> + * memblock_isolate_memory - isolate given range in memblock.memory
> + * @base: base of range to isolate
> + * @size: size of range to isolate
> + *
> + * Isolates the given range in memblock.memory so that it does not share any
> + * region with other ranges.
> + *
> + * Return:
> + * 0 on success, -errno on failure.
> + */
> +
> +int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
> +{
> + int start_rgn, end_rgn;
> +
> + return memblock_isolate_range(&memblock.memory, base, size,
> + &start_rgn, &end_rgn);
> +}
> +
> static int __init_memblock memblock_remove_range(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size)
> {
> --
> 2.37.2
>

--
Sincerely yours,
Mike.