Vishal Verma wrote:
> The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to
> 'memblock_size' chunks of memory being added. Adding a larger span of
> memory precludes memmap_on_memory semantics.
>
> For users of hotplug such as kmem, large amounts of memory might get
> added from the CXL subsystem. In some cases, this amount may exceed the
> available 'main memory' to store the memmap for the memory being added.
> In this case, it is useful to have a way to place the memmap on the
> memory being added, even if it means splitting the addition into
> memblock-sized chunks.
>
> Change add_memory_resource() to loop over memblock-sized chunks of
> memory if caller requested memmap_on_memory, and if other conditions for
> it are met. Teach try_remove_memory() to also expect that a memory
> range being removed might have been split up into memblock sized chunks,
> and to loop through those as needed.
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> ---
> mm/memory_hotplug.c | 162 ++++++++++++++++++++++++++++++++--------------------
> 1 file changed, 99 insertions(+), 63 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index f8d3e7427e32..77ec6f15f943 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1380,6 +1380,44 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
> return arch_supports_memmap_on_memory(vmemmap_size);
> }
>
> +static int add_memory_create_devices(int nid, struct memory_group *group,
> + u64 start, u64 size, mhp_t mhp_flags)
> +{
> + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
> + struct vmem_altmap mhp_altmap = {
> + .base_pfn = PHYS_PFN(start),
> + .end_pfn = PHYS_PFN(start + size - 1),
> + };
> + int ret;
> +
> + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) {
> + mhp_altmap.free = memory_block_memmap_on_memory_pages();
> + params.altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL);
> + if (!params.altmap)
> + return -ENOMEM;
> +
> + memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap));
Isn't this just open coded kmemdup()?
Other than that, I am not seeing anything else to comment on, you can add:
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
