On Thu, Jul 27, 2023 at 09:46:22PM +0100, Usama Arif 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>
> ---
> include/linux/memblock.h | 7 +++++++
> mm/memblock.c | 32 ++++++++++++++++++++++++++------
> 2 files changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f71ff9f0ec81..7f9d06c08592 100644
> --e a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -47,6 +47,7 @@ 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 */
> + MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call reserve_bootmem_region for this region */
The comment should reflect what it does, not how.
> };
>
> /**
> @@ -125,6 +126,7 @@ 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_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
Please spell out reserved here.
> void memblock_free_all(void);
> void memblock_free(void *ptr, size_t size);
> @@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
> return m->flags & MEMBLOCK_NOMAP;
> }
>
> +static inline bool memblock_is_noinit(struct memblock_region *m)
> +{
> + return m->flags & MEMBLOCK_RSRV_NOINIT;
> +}
> +
> static inline bool memblock_is_driver_managed(struct memblock_region *m)
> {
> return m->flags & MEMBLOCK_DRIVER_MANAGED;
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4fd431d16ef2..3a15708af3b6 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -997,6 +997,22 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
> return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
> }
>
> +/**
> + * memblock_rsrv_mark_noinit - Mark a reserved memory region with flag MEMBLOCK_RSRV_NOINIT.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * For memory regions marked with %MEMBLOCK_RSRV_NOINIT, reserve_bootmem_region
> + * is not called during memmap_init_reserved_pages, hence struct pages are not
> + * initialized for this region.
Here as well, the part of how is much less important. Here you should
emphasize that struct pages for MEMBLOCK_RSRV_NOINIT regions are not
initialized.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size)
> +{
> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_RSRV_NOINIT, 1);
> +}
> +
> static bool should_skip_region(struct memblock_type *type,
> struct memblock_region *m,
> int nid, int flags)
> @@ -2113,13 +2129,17 @@ static void __init memmap_init_reserved_pages(void)
> memblock_set_node(start, end, &memblock.reserved, nid);
> }
>
> - /* initialize struct pages for the reserved regions */
> + /*
> + * initialize struct pages for reserved regions that don't have
> + * the MEMBLOCK_RSRV_NOINIT flag set
> + */
> for_each_reserved_mem_region(region) {
> - nid = memblock_get_region_node(region);
> - start = region->base;
> - end = start + region->size;
> -
> - reserve_bootmem_region(start, end, nid);
> + if (!memblock_is_noinit(region)) {
> + nid = memblock_get_region_node(region);
> + start = region->base;
> + end = start + region->size;
Please keep the empty line here
> + reserve_bootmem_region(start, end, nid);
> + }
> }
> }
>
> --
> 2.25.1
>
--
Sincerely yours,
Mike.
