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Message-ID: <cd7c5f6b-d668-4fab-8e7e-4f41018067c5@redhat.com>
Date: Thu, 14 Dec 2023 10:10:43 +0100
From: David Hildenbrand <david@...hat.com>
To: Vishal Verma <vishal.l.verma@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Dave Jiang <dave.jiang@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Oscar Salvador <osalvador@...e.de>
Cc: linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
linux-cxl@...r.kernel.org,
Dave Hansen <dave.hansen@...ux.intel.com>,
Huang Ying <ying.huang@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-mm@...ck.org, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v5 3/4] mm/memory_hotplug: export
mhp_supports_memmap_on_memory()
On 14.12.23 08:37, Vishal Verma wrote:
> In preparation for adding sysfs ABI to toggle memmap_on_memory semantics
> for drivers adding memory, export the mhp_supports_memmap_on_memory()
> helper. This allows drivers to check if memmap_on_memory support is
> available before trying to request it, and display an appropriate
> message if it isn't available. As part of this, remove the size argument
> to this - with recent updates to allow memmap_on_memory for larger
> ranges, and the internal splitting of altmaps into respective memory
> blocks, the size argument is meaningless.
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Huang Ying <ying.huang@...el.com>
> Suggested-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>
> ---
> include/linux/memory_hotplug.h | 6 ++++++
> mm/memory_hotplug.c | 17 ++++++-----------
> 2 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 7d2076583494..ebc9d528f00c 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -121,6 +121,7 @@ struct mhp_params {
>
> bool mhp_range_allowed(u64 start, u64 size, bool need_mapping);
> struct range mhp_get_pluggable_range(bool need_mapping);
> +bool mhp_supports_memmap_on_memory(void);
>
> /*
> * Zone resizing functions
> @@ -262,6 +263,11 @@ static inline bool movable_node_is_enabled(void)
> return false;
> }
>
> +static bool mhp_supports_memmap_on_memory(void)
> +{
> + return false;
> +}
> +
> static inline void pgdat_kswapd_lock(pg_data_t *pgdat) {}
> static inline void pgdat_kswapd_unlock(pg_data_t *pgdat) {}
> static inline void pgdat_kswapd_lock_init(pg_data_t *pgdat) {}
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 926e1cfb10e9..751664c519f7 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1325,7 +1325,7 @@ static inline bool arch_supports_memmap_on_memory(unsigned long vmemmap_size)
> }
> #endif
>
> -static bool mhp_supports_memmap_on_memory(unsigned long size)
> +bool mhp_supports_memmap_on_memory(void)
> {
> unsigned long vmemmap_size = memory_block_memmap_size();
> unsigned long memmap_pages = memory_block_memmap_on_memory_pages();
> @@ -1334,17 +1334,11 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
> * Besides having arch support and the feature enabled at runtime, we
> * need a few more assumptions to hold true:
> *
> - * a) We span a single memory block: memory onlining/offlinin;g happens
> - * in memory block granularity. We don't want the vmemmap of online
> - * memory blocks to reside on offline memory blocks. In the future,
> - * we might want to support variable-sized memory blocks to make the
> - * feature more versatile.
> - *
> - * b) The vmemmap pages span complete PMDs: We don't want vmemmap code
> + * a) The vmemmap pages span complete PMDs: We don't want vmemmap code
> * to populate memory from the altmap for unrelated parts (i.e.,
> * other memory blocks)
> *
> - * c) The vmemmap pages (and thereby the pages that will be exposed to
> + * b) The vmemmap pages (and thereby the pages that will be exposed to
> * the buddy) have to cover full pageblocks: memory onlining/offlining
> * code requires applicable ranges to be page-aligned, for example, to
> * set the migratetypes properly.
> @@ -1356,7 +1350,7 @@ 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.
> */
> - if (!mhp_memmap_on_memory() || size != memory_block_size_bytes())
> + if (!mhp_memmap_on_memory())
> return false;
>
> /*
> @@ -1379,6 +1373,7 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
>
> return arch_supports_memmap_on_memory(vmemmap_size);
> }
> +EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory);
>
> static void __ref remove_memory_blocks_and_altmaps(u64 start, u64 size)
> {
> @@ -1512,7 +1507,7 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> * Self hosted memmap array
> */
> if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) &&
> - mhp_supports_memmap_on_memory(memory_block_size_bytes())) {
> + mhp_supports_memmap_on_memory()) {
> ret = create_altmaps_and_memory_blocks(nid, group, start, size);
> if (ret)
> goto error;
>
Acked-by: David Hildenbrand <david@...hat.com>
--
Cheers,
David / dhildenb
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