"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> writes:
> Add a new kconfig option that can be selected if we want to allow
> pageblock alignment by reserving pages in the vmemmap altmap area.
> This implies we will be reserving some pages for every memoryblock
> This also allows the memmap on memory feature to be widely useful
> with different memory block size values.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> ---
> mm/Kconfig | 9 +++++++
> mm/memory_hotplug.c | 59 +++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 58 insertions(+), 10 deletions(-)
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 932349271e28..88a1472b2086 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -570,6 +570,15 @@ config MHP_MEMMAP_ON_MEMORY
> depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
> depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>
> +config MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY
> + bool "Allow Reserving pages for page block aligment"
> + depends on MHP_MEMMAP_ON_MEMORY
> + help
> + This option allows memmap on memory feature to be more useful
> + with different memory block sizes. This is achieved by marking some pages
> + in each memory block as reserved so that we can get page-block alignment
> + for the remaining pages.
> +
> endif # MEMORY_HOTPLUG
>
> config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 07c99b0cc371..f36aec1f7626 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1252,15 +1252,17 @@ static inline bool arch_supports_memmap_on_memory(unsigned long size)
> {
> unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
> unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
> - unsigned long remaining_size = size - vmemmap_size;
>
> - return IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> - IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
> + return IS_ALIGNED(vmemmap_size, PMD_SIZE);
> }
> #endif
>
> static bool mhp_supports_memmap_on_memory(unsigned long size)
> {
> + unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
> + unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
> + unsigned long remaining_size = size - vmemmap_size;
> +
> /*
> * Besides having arch support and the feature enabled at runtime, we
> * need a few more assumptions to hold true:
> @@ -1287,9 +1289,30 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
> * altmap as an alternative source of memory, and we do not exactly
> * populate a single PMD.
> */
> - return mhp_memmap_on_memory() &&
> - size == memory_block_size_bytes() &&
> - arch_supports_memmap_on_memory(size);
> + if (!mhp_memmap_on_memory() || size != memory_block_size_bytes())
> + return false;
> + /*
> + * Without page reservation remaining pages should be pageblock aligned.
> + */
> + if (!IS_ENABLED(CONFIG_MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY) &&
> + !IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT)))
> + return false;
> +
> + return arch_supports_memmap_on_memory(size);
> +}
> +
> +static inline unsigned long memory_block_align_base(unsigned long size)
> +{
> + if (IS_ENABLED(CONFIG_MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY)) {
> + unsigned long align;
> + unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
> + unsigned long vmemmap_size;
> +
> + vmemmap_size = (nr_vmemmap_pages * sizeof(struct page)) >> PAGE_SHIFT;
DIV_ROUND_UP()?
> + align = pageblock_align(vmemmap_size) - vmemmap_size;
> + return align;
> + } else
> + return 0;
> }
>
> /*
> @@ -1302,7 +1325,11 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> {
> struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
> enum memblock_flags memblock_flags = MEMBLOCK_NONE;
> - struct vmem_altmap mhp_altmap = {};
> + struct vmem_altmap mhp_altmap = {
> + .base_pfn = PHYS_PFN(res->start),
> + .end_pfn = PHYS_PFN(res->end),
> + .reserve = memory_block_align_base(resource_size(res)),
> + };
> struct memory_group *group = NULL;
> u64 start, size;
> bool new_node = false;
> @@ -1347,8 +1374,7 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> */
> if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
> if (mhp_supports_memmap_on_memory(size)) {
> - mhp_altmap.free = PHYS_PFN(size);
> - mhp_altmap.base_pfn = PHYS_PFN(start);
> + mhp_altmap.free = PHYS_PFN(size) - mhp_altmap.reserve;
> params.altmap = &mhp_altmap;
> }
> /* fallback to not using altmap */
> @@ -1360,7 +1386,7 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> goto error;
>
> /* create memory block devices after memory was added */
> - ret = create_memory_block_devices(start, size, mhp_altmap.alloc,
> + ret = create_memory_block_devices(start, size, mhp_altmap.alloc + mhp_altmap.reserve,
> group);
> if (ret) {
> arch_remove_memory(start, size, NULL);
> @@ -2260,3 +2286,16 @@ int offline_and_remove_memory(u64 start, u64 size)
> }
> EXPORT_SYMBOL_GPL(offline_and_remove_memory);
> #endif /* CONFIG_MEMORY_HOTREMOVE */
> +
> +static int __init memory_hotplug_init(void)
> +{
> +
> + if (IS_ENABLED(CONFIG_MHP_RESERVE_PAGES_MEMMAP_ON_MEMORY) &&
> + mhp_memmap_on_memory()) {
> + pr_info("Memory hotplug will reserve %ld pages in each memory block\n",
> + memory_block_align_base(memory_block_size_bytes()));
> +
> + }
> + return 0;
> +}
> +module_init(memory_hotplug_init);
