Re: [PATCH 18/26] mm/memblock: Add MEMBLOCK_INSPECT flag

Mike Rapoport
2025-12-29T06:56:45Z

Hi Eugen,

On Wed, Nov 19, 2025 at 05:44:19PM +0200, Eugen Hristev wrote:
> This memblock flag indicates that a specific block is registered
> into an inspection table.
> The block can be marked for inspection using memblock_mark_inspect()
> and cleared with memblock_clear_inspect()

Can you explain why memblock should treat memory registered for inspection
differently?

> Signed-off-by: Eugen Hristev <eugen.hristev@linaro.org>
> ---
> include/linux/memblock.h | 7 +++++++
> mm/memblock.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 43 insertions(+)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 221118b5a16e..c3e55a4475cf 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -51,6 +51,10 @@ extern unsigned long long max_possible_pfn;
> * memory reservations yet, so we get scratch memory from the previous
> * kernel that we know is good to use. It is the only memory that
> * allocations may happen from in this phase.
> + * @MEMBLOCK_INSPECT: memory region is annotated in kernel memory inspection
> + * table. This means a dedicated entry will be created for this region which
> + * will contain the memory's address and size. This allows kernel inspectors
> + * to retrieve the memory.
> */
> enum memblock_flags {
> MEMBLOCK_NONE = 0x0, /* No special request */
> @@ -61,6 +65,7 @@ enum memblock_flags {
> MEMBLOCK_RSRV_NOINIT = 0x10, /* don't initialize struct pages */
> MEMBLOCK_RSRV_KERN = 0x20, /* memory reserved for kernel use */
> MEMBLOCK_KHO_SCRATCH = 0x40, /* scratch memory for kexec handover */
> + MEMBLOCK_INSPECT = 0x80, /* memory selected for kernel inspection */
> };
>
> /**
> @@ -149,6 +154,8 @@ unsigned long memblock_addrs_overlap(phys_addr_t base1, phys_addr_t size1,
> bool memblock_overlaps_region(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size);
> bool memblock_validate_numa_coverage(unsigned long threshold_bytes);
> +int memblock_mark_inspect(phys_addr_t base, phys_addr_t size);
> +int memblock_clear_inspect(phys_addr_t base, phys_addr_t size);
> int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e23e16618e9b..a5df5ab286e5 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -17,6 +17,7 @@
> #include <linux/seq_file.h>
> #include <linux/memblock.h>
> #include <linux/mutex.h>
> +#include <linux/meminspect.h>
>
> #ifdef CONFIG_KEXEC_HANDOVER
> #include <linux/libfdt.h>
> @@ -1016,6 +1017,40 @@ static int __init_memblock memblock_setclr_flag(struct memblock_type *type,
> return 0;
> }
>
> +/**
> + * memblock_mark_inspect - Mark inspectable memory with flag MEMBLOCK_INSPECT.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_mark_inspect(phys_addr_t base, phys_addr_t size)
> +{
> + int ret;
> +
> + ret = memblock_setclr_flag(&memblock.memory, base, size, 1, MEMBLOCK_INSPECT);
> + if (ret)
> + return ret;
> +
> + meminspect_lock_register_pa(base, size);
> +
> + return 0;
> +}
> +
> +/**
> + * memblock_clear_inspect - Clear flag MEMBLOCK_INSPECT for a specified region.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_clear_inspect(phys_addr_t base, phys_addr_t size)
> +{
> + meminspect_lock_unregister_pa(base, size);
> +
> + return memblock_setclr_flag(&memblock.memory, base, size, 0, MEMBLOCK_INSPECT);
> +}
> +
> /**
> * memblock_mark_hotplug - Mark hotpluggable memory with flag MEMBLOCK_HOTPLUG.
> * @base: the base phys addr of the region
> @@ -2704,6 +2739,7 @@ static const char * const flagname[] = {
> [ilog2(MEMBLOCK_RSRV_NOINIT)] = "RSV_NIT",
> [ilog2(MEMBLOCK_RSRV_KERN)] = "RSV_KERN",
> [ilog2(MEMBLOCK_KHO_SCRATCH)] = "KHO_SCRATCH",
> + [ilog2(MEMBLOCK_INSPECT)] = "INSPECT",
> };
>
> static int memblock_debug_show(struct seq_file *m, void *private)
> --
> 2.43.0
>

--
Sincerely yours,
Mike.