Re: [v3 3/4] memblock: introduce MEMBLOCK_RSRV_NOINIT_VMEMMAP flag

[Muchun Song]

> On Aug 25, 2023, at 19:18, Usama Arif <usama.arif@xxxxxxxxxxxxx> wrote:
> 
> For reserved memory regions marked with this flag,
> reserve_bootmem_region is not called during memmap_init_reserved_pages.
> This can be used to avoid struct page initialization for
> regions which won't need them, for e.g. hugepages with
> HVO enabled.
> 
> Signed-off-by: Usama Arif <usama.arif@xxxxxxxxxxxxx>

Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>

One nit below.

> ---
> include/linux/memblock.h | 10 ++++++++++
> mm/memblock.c            | 32 +++++++++++++++++++++++++++-----
> 2 files changed, 37 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f71ff9f0ec81..6d681d053880 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -40,6 +40,8 @@ extern unsigned long long max_possible_pfn;
>  * via a driver, and never indicated in the firmware-provided memory map as
>  * system RAM. This corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED in the
>  * kernel resource tree.
> + * @MEMBLOCK_RSRV_NOINIT_VMEMMAP: memory region for which struct pages are
> + * not initialized (only for reserved regions).

We have a more detailed explanation here.

>  */
> enum memblock_flags {
> 	MEMBLOCK_NONE = 0x0, /* No special request */
> @@ -47,6 +49,8 @@ enum memblock_flags {
> 	MEMBLOCK_MIRROR = 0x2, /* mirrored region */
> 	MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
> 	MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
> +	/* don't initialize struct pages associated with this reserver memory block */

Those comments right after the macros here seem like a brief explanation.
To keep the consistent with others, maybe "don't initialize struct pages"
is enough? At least, a detailed one is redundant and repetitive compared
with the above one.

> +	MEMBLOCK_RSRV_NOINIT_VMEMMAP = 0x10,
> };