On Fri, Apr 16, 2021 at 12:51:31PM +0200, David Hildenbrand wrote:
> The thing is: move_pfn_range_to_zone() in case of ordinary online_pages()
> won't touch the pages but only the memmap. The memmap has a proper kasan
> shadow already. Pages won't be touched before exposing them to the page
> allocator via generic_online_pages().
>
> This is different in this case :)
Meh, yeah, I missed that.
My brain went almost friday-mood, but this should be the complete diff then:
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index f209925a5d4e..2e2b2f654f0a 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -173,16 +173,72 @@ static int memory_block_online(struct memory_block *mem)
{
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
+ unsigned long nr_vmemmap_pages = mem->nr_vmemmap_pages;
+ struct zone *zone;
+ int ret;
+
+ zone = zone_for_pfn_range(mem->online_type, mem->nid, start_pfn,
nr_pages);
+
+ /*
+ * Although vmemmap pages have a different lifecycle than the pages
+ * they describe (they remain until the memory is unplugged), doing
+ * their initialization and accounting at memory onlining/offlining
+ * stage simplifies things a lot.
+ */
+ if (nr_vmemmap_pages) {
+ ret = mhp_init_memmap_on_memory(start_pfn, nr_vmemmap_pages,
zone);
+ if (ret)
+ return ret;
+ }
+
+ ret = online_pages(start_pfn + nr_vmemmap_pages,
+ nr_pages - nr_vmemmap_pages, zone);
+ if (ret) {
+ if (nr_vmemmap_pages)
+ mhp_deinit_memmap_on_memory(start_pfn,
nr_vmemmap_pages);
+ return ret;
+ }
+
+ /*
+ * Account once onlining succeeded. If the zone was unpopulated, it is
+ * now already properly populated.
+ */
+ if (nr_vmemmap_pages)
+ adjust_present_page_count(zone, nr_vmemmap_pages);
- return online_pages(start_pfn, nr_pages, mem->online_type, mem->nid);
+ return ret;
}
static int memory_block_offline(struct memory_block *mem)
{
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
+ unsigned long nr_vmemmap_pages = mem->nr_vmemmap_pages;
+ struct zone *zone;
+ int ret;
+
+ zone = page_zone(pfn_to_page(start_pfn));
+
+ /*
+ * Unaccount before offlining, such that unpopulated zone and kthreads
+ * can properly be torn down in offline_pages().
+ */
+ if (nr_vmemmap_pages)
+ adjust_present_page_count(zone, -nr_vmemmap_pages);
- return offline_pages(start_pfn, nr_pages);
+ ret = offline_pages(start_pfn + nr_vmemmap_pages,
+ nr_pages - nr_vmemmap_pages);
+ if (ret) {
+ /* offline_pages() failed. Account back. */
+ if (nr_vmemmap_pages)
+ adjust_present_page_count(zone, nr_vmemmap_pages);
+ return ret;
+ }
+
+ if (nr_vmemmap_pages)
+ mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);
+
+ return ret;
}
/*
@@ -576,7 +632,8 @@ int register_memory(struct memory_block *memory)
return ret;
}
-static int init_memory_block(unsigned long block_id, unsigned long state)
+static int init_memory_block(unsigned long block_id, unsigned long state,
+ unsigned long nr_vmemmap_pages)
{
struct memory_block *mem;
int ret = 0;
@@ -593,6 +650,7 @@ static int init_memory_block(unsigned long block_id,
unsigned long state)
mem->start_section_nr = block_id * sections_per_block;
mem->state = state;
mem->nid = NUMA_NO_NODE;
+ mem->nr_vmemmap_pages = nr_vmemmap_pages;
ret = register_memory(mem);
@@ -612,7 +670,7 @@ static int add_memory_block(unsigned long base_section_nr)
if (section_count == 0)
return 0;
return init_memory_block(memory_block_id(base_section_nr),
- MEM_ONLINE);
+ MEM_ONLINE, 0);
}
static void unregister_memory(struct memory_block *memory)
@@ -634,7 +692,8 @@ static void unregister_memory(struct memory_block *memory)
*
* Called under device_hotplug_lock.
*/
-int create_memory_block_devices(unsigned long start, unsigned long size)
+int create_memory_block_devices(unsigned long start, unsigned long size,
+ unsigned long vmemmap_pages)
{
const unsigned long start_block_id = pfn_to_block_id(PFN_DOWN(start));
unsigned long end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
@@ -647,7 +706,7 @@ int create_memory_block_devices(unsigned long start,
unsigned long size)
return -EINVAL;
for (block_id = start_block_id; block_id != end_block_id; block_id++) {
- ret = init_memory_block(block_id, MEM_OFFLINE);
+ ret = init_memory_block(block_id, MEM_OFFLINE, vmemmap_pages);
if (ret)
break;
}
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 4da95e684e20..97e92e8b556a 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -29,6 +29,11 @@ struct memory_block {
int online_type; /* for passing data to online routine */
int nid; /* NID for this memory block */
struct device dev;
+ /*
+ * Number of vmemmap pages. These pages
+ * lay at the beginning of the memory block.
+ */
+ unsigned long nr_vmemmap_pages;
};
int arch_get_memory_phys_device(unsigned long start_pfn);
@@ -80,7 +85,8 @@ static inline int memory_notify(unsigned long val, void *v)
#else
extern int register_memory_notifier(struct notifier_block *nb);
extern void unregister_memory_notifier(struct notifier_block *nb);
-int create_memory_block_devices(unsigned long start, unsigned long size);
+int create_memory_block_devices(unsigned long start, unsigned long size,
+ unsigned long vmemmap_pages);
void remove_memory_block_devices(unsigned long start, unsigned long size);
extern void memory_dev_init(void);
extern int memory_notify(unsigned long val, void *v);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 7288aa5ef73b..28f32fd00fe9 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -55,6 +55,14 @@ typedef int __bitwise mhp_t;
*/
#define MHP_MERGE_RESOURCE ((__force mhp_t)BIT(0))
+/*
+ * We want memmap (struct page array) to be self contained.
+ * To do so, we will use the beginning of the hot-added range to build
+ * the page tables for the memmap array that describes the entire range.
+ * Only selected architectures support it with SPARSE_VMEMMAP.
+ */
+#define MHP_MEMMAP_ON_MEMORY ((__force mhp_t)BIT(1))
+
/*
* Extended parameters for memory hotplug:
* altmap: alternative allocator for memmap array (optional)
@@ -99,9 +107,13 @@ static inline void zone_seqlock_init(struct zone *zone)
extern int zone_grow_free_lists(struct zone *zone, unsigned long new_nr_pages);
extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages);
extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
+extern void adjust_present_page_count(struct zone *zone, long nr_pages);
/* VM interface that may be used by firmware interface */
+extern int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
+ struct zone *zone);
+extern void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long
nr_pages);
extern int online_pages(unsigned long pfn, unsigned long nr_pages,
- int online_type, int nid);
+ struct zone *zone);
extern struct zone *test_pages_in_a_zone(unsigned long start_pfn,
unsigned long end_pfn);
extern void __offline_isolated_pages(unsigned long start_pfn,
@@ -359,6 +371,7 @@ extern struct zone *zone_for_pfn_range(int online_type, int
nid, unsigned start_
extern int arch_create_linear_mapping(int nid, u64 start, u64 size,
struct mhp_params *params);
void arch_remove_linear_mapping(u64 start, u64 size);
+extern bool mhp_supports_memmap_on_memory(unsigned long size);
#endif /* CONFIG_MEMORY_HOTPLUG */
#endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index f5b464daeeca..45a79da89c5f 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -17,7 +17,7 @@ struct device;
* @alloc: track pages consumed, private to vmemmap_populate()
*/
struct vmem_altmap {
- const unsigned long base_pfn;
+ unsigned long base_pfn;
const unsigned long end_pfn;
const unsigned long reserve;
unsigned long free;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 47946cec7584..76f4ca5ed230 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -427,6 +427,11 @@ enum zone_type {
* techniques might use alloc_contig_range() to hide previously
* exposed pages from the buddy again (e.g., to implement some sort
* of memory unplug in virtio-mem).
+ * 6. Memory-hotplug: when using memmap_on_memory and onlining the
memory
+ * to the MOVABLE zone, the vmemmap pages are also placed in such
+ * zone. Such pages cannot be really moved around as they are
+ * self-stored in the range, but they are treated as movable when
+ * the range they describe is about to be offlined.
*
* In general, no unmovable allocations that degrade memory offlining
* should end up in ZONE_MOVABLE. Allocators (like alloc_contig_range())
@@ -1378,10 +1383,8 @@ static inline int online_section_nr(unsigned long nr)
#ifdef CONFIG_MEMORY_HOTPLUG
void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
-#ifdef CONFIG_MEMORY_HOTREMOVE
void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
#endif
-#endif
static inline struct mem_section *__pfn_to_section(unsigned long pfn)
{
diff --git a/mm/Kconfig b/mm/Kconfig
index 24c045b24b95..febf805000f8 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -183,6 +183,11 @@ config MEMORY_HOTREMOVE
depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
depends on MIGRATION
+config MHP_MEMMAP_ON_MEMORY
+ def_bool y
+ depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
+ depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
+
# Heavily threaded applications may benefit from splitting the mm-wide
# page_table_lock, so that faults on different parts of the user address
# space can be handled with less contention: split it at this NR_CPUS.
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index d05056b3c173..489e2b538ff8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -42,6 +42,8 @@
#include "internal.h"
#include "shuffle.h"
+static bool memmap_on_memory;
+
/*
* online_page_callback contains pointer to current page onlining function.
* Initially it is generic_online_page(). If it is required it could be
@@ -641,7 +643,12 @@ EXPORT_SYMBOL_GPL(generic_online_page);
static void online_pages_range(unsigned long start_pfn, unsigned long nr_pages)
{
const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn;
+ unsigned long pfn = start_pfn;
+
+ while (!IS_ALIGNED(pfn, MAX_ORDER_NR_PAGES)) {
+ (*online_page_callback)(pfn_to_page(pfn), pageblock_order);
+ pfn += pageblock_nr_pages;
+ }
/*
* Online the pages in MAX_ORDER - 1 aligned chunks. The callback might
@@ -649,7 +656,7 @@ static void online_pages_range(unsigned long start_pfn,
unsigned long nr_pages)
* later). We account all pages as being online and belonging to this
* zone ("present").
*/
- for (pfn = start_pfn; pfn < end_pfn; pfn += MAX_ORDER_NR_PAGES)
+ for (; pfn < end_pfn; pfn += MAX_ORDER_NR_PAGES)
(*online_page_callback)(pfn_to_page(pfn), MAX_ORDER - 1);
/* mark all involved sections as online */
@@ -829,7 +836,11 @@ struct zone * zone_for_pfn_range(int online_type, int nid,
unsigned start_pfn,
return default_zone_for_pfn(nid, start_pfn, nr_pages);
}
-static void adjust_present_page_count(struct zone *zone, long nr_pages)
+/*
+ * This function should only be called by memory_block_{online,offline},
+ * and {online,offline}_pages.
+ */
+void adjust_present_page_count(struct zone *zone, long nr_pages)
{
unsigned long flags;
@@ -839,12 +850,56 @@ static void adjust_present_page_count(struct zone *zone,
long nr_pages)
pgdat_resize_unlock(zone->zone_pgdat, &flags);
}
-int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
- int online_type, int nid)
+int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
+ struct zone *zone)
+{
+ unsigned long end_pfn = pfn + nr_pages;
+ int ret;
+
+ ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
+ if (ret)
+ return ret;
+
+ /*
+ * Initialize vmemmap pages with the corresponding node, zone links set.
+ */
+ move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
+
+ /*
+ * It might be that the vmemmap_pages fully span sections. If that is
+ * the case, mark those sections online here as otherwise they will be
+ * left offline.
+ */
+ if (nr_pages >= PAGES_PER_SECTION)
+ online_mem_sections(pfn, ALIGN_DOWN(end_pfn,
PAGES_PER_SECTION));
+
+ return ret;
+}
+
+void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long nr_pages)
+{
+ unsigned long end_pfn = pfn + nr_pages;
+ /*
+ * The pages associated with this vmemmap have been offlined, so
+ * we can reset its state here.
+ */
+ remove_pfn_range_from_zone(page_zone(pfn_to_page(pfn)), pfn, nr_pages);
+ kasan_remove_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
+
+ /*
+ * It might be that the vmemmap_pages fully span sections. If that is
+ * the case, mark those sections offline here as otherwise they will be
+ * left online.
+ */
+ if (nr_pages >= PAGES_PER_SECTION)
+ offline_mem_sections(pfn, ALIGN_DOWN(end_pfn,
PAGES_PER_SECTION));
+}
+
+int __ref online_pages(unsigned long pfn, unsigned long nr_pages, struct zone
*zone)
{
unsigned long flags;
- struct zone *zone;
int need_zonelists_rebuild = 0;
+ const int nid = zone_to_nid(zone);
int ret;
struct memory_notify arg;
@@ -861,7 +916,6 @@ int __ref online_pages(unsigned long pfn, unsigned long
nr_pages,
mem_hotplug_begin();
/* associate pfn range with the zone */
- zone = zone_for_pfn_range(online_type, nid, pfn, nr_pages);
move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_ISOLATE);
arg.start_pfn = pfn;
@@ -1075,6 +1129,45 @@ static int online_memory_block(struct memory_block *mem,
void *arg)
return device_online(&mem->dev);
}
+bool mhp_supports_memmap_on_memory(unsigned long size)
+{
+ unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
+ 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:
+ *
+ * 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
+ * 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
+ * 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.
+ *
+ * TODO: Although we have a check here to make sure that vmemmap pages
+ * fully populate a PMD, it is not the right place to check for
+ * this. A much better solution involves improving vmemmap code
+ * to fallback to base pages when trying to populate vmemmap using
+ * altmap as an alternative source of memory, and we do not
exactly
+ * populate a single PMD.
+ */
+ return memmap_on_memory &&
+ IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
+ size == memory_block_size_bytes() &&
+ IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
+ IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
+}
+
/*
* NOTE: The caller must call lock_device_hotplug() to serialize hotplug
* and online/offline operations (triggered e.g. by sysfs).
@@ -1084,6 +1177,7 @@ static int online_memory_block(struct memory_block *mem,
void *arg)
int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
{
struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
+ struct vmem_altmap mhp_altmap = {};
u64 start, size;
bool new_node = false;
int ret;
@@ -1110,13 +1204,26 @@ int __ref add_memory_resource(int nid, struct resource
*res, mhp_t mhp_flags)
goto error;
new_node = ret;
+ /*
+ * Self hosted memmap array
+ */
+ if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
+ if (!mhp_supports_memmap_on_memory(size)) {
+ ret = -EINVAL;
+ goto error;
+ }
+ mhp_altmap.free = PHYS_PFN(size);
+ mhp_altmap.base_pfn = PHYS_PFN(start);
+ params.altmap = &mhp_altmap;
+ }
+
/* call arch's memory hotadd */
ret = arch_add_memory(nid, start, size, ¶ms);
if (ret < 0)
goto error;
/* create memory block devices after memory was added */
- ret = create_memory_block_devices(start, size);
+ ret = create_memory_block_devices(start, size, mhp_altmap.alloc);
if (ret) {
arch_remove_memory(nid, start, size, NULL);
goto error;
@@ -1762,6 +1869,14 @@ static int check_memblock_offlined_cb(struct
memory_block *mem, void *arg)
return 0;
}
+static int get_nr_vmemmap_pages_cb(struct memory_block *mem, void *arg)
+{
+ /*
+ * If not set, continue with the next block.
+ */
+ return mem->nr_vmemmap_pages;
+}
+
static int check_cpu_on_node(pg_data_t *pgdat)
{
int cpu;
@@ -1836,6 +1951,9 @@ EXPORT_SYMBOL(try_offline_node);
static int __ref try_remove_memory(int nid, u64 start, u64 size)
{
int rc = 0;
+ struct vmem_altmap mhp_altmap = {};
+ struct vmem_altmap *altmap = NULL;
+ unsigned long nr_vmemmap_pages;
BUG_ON(check_hotplug_memory_range(start, size));
@@ -1848,6 +1966,31 @@ static int __ref try_remove_memory(int nid, u64 start,
u64 size)
if (rc)
return rc;
+ /*
+ * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in
+ * the same granularity it was added - a single memory block.
+ */
+ if (memmap_on_memory) {
+ nr_vmemmap_pages = walk_memory_blocks(start, size, NULL,
+ get_nr_vmemmap_pages_cb);
+ if (nr_vmemmap_pages) {
+ if (size != memory_block_size_bytes()) {
+ pr_warn("Refuse to remove %#llx - %#llx,"
+ "wrong granularity\n",
+ start, start + size);
+ return -EINVAL;
+ }
+
+ /*
+ * Let remove_pmd_table->free_hugepage_table do the
+ * right thing if we used vmem_altmap when hot-adding
+ * the range.
+ */
+ mhp_altmap.alloc = nr_vmemmap_pages;
+ altmap = &mhp_altmap;
+ }
+ }
+
/* remove memmap entry */
firmware_map_remove(start, start + size, "System RAM");
@@ -1859,7 +2002,7 @@ static int __ref try_remove_memory(int nid, u64 start,
u64 size)
mem_hotplug_begin();
- arch_remove_memory(nid, start, size, NULL);
+ arch_remove_memory(nid, start, size, altmap);
if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
memblock_free(start, size);
diff --git a/mm/sparse.c b/mm/sparse.c
index 7bd23f9d6cef..8e96cf00536b 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -623,7 +623,6 @@ void online_mem_sections(unsigned long start_pfn, unsigned
long end_pfn)
}
}
-#ifdef CONFIG_MEMORY_HOTREMOVE
/* Mark all memory sections within the pfn range as offline */
void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
{
@@ -644,7 +643,6 @@ void offline_mem_sections(unsigned long start_pfn, unsigned
long end_pfn)
ms->section_mem_map &= ~SECTION_IS_ONLINE;
}
}
-#endif
#ifdef CONFIG_SPARSEMEM_VMEMMAP
static struct page * __meminit populate_section_memmap(unsigned long pfn,
--
Oscar Salvador
SUSE L3
