[PATCH 4/5] Hot-remove implementation for arm64

Andrea Reale
2017-04-11T14:55:59Z

- arch_remove_memory interface
- kernel page tables cleanup
- vmemmap_free implementation for arm64

Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
Signed-off-by: Maciej Bielski <m.bielski@virtualopensystems.com>
---
arch/arm64/Kconfig | 3 +
arch/arm64/include/asm/mmu.h | 4 +
arch/arm64/include/asm/pgtable.h | 15 ++
arch/arm64/mm/init.c | 32 +++-
arch/arm64/mm/mmu.c | 390 ++++++++++++++++++++++++++++++++++++++-
5 files changed, 438 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fa71d94..83b8bb5 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -624,6 +624,9 @@ config ARCH_ENABLE_MEMORY_HOTPLUG
depends on !NUMA
def_bool y

+config ARCH_ENABLE_MEMORY_HOTREMOVE
+ def_bool y
+
# Common NUMA Features
config NUMA
bool "Numa Memory Allocation and Scheduler Support"
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 8eb31db..2cf2115 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -39,6 +39,10 @@ extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
#ifdef CONFIG_MEMORY_HOTPLUG
extern void hotplug_paging(phys_addr_t start, phys_addr_t size);
+#ifdef CONFIG_MEMORY_HOTREMOVE
+extern void remove_pagetable(unsigned long start,
+ unsigned long end, bool direct);
+#endif
#endif

#endif
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 0eef606..194cb3e 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -399,6 +399,11 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)
return pmd_val(pmd) & PHYS_MASK & (s32)PAGE_MASK;
}

+static inline unsigned long pmd_page_vaddr(pmd_t pmd)
+{
+ return (unsigned long) __va(pmd_page_paddr(pmd));
+}
+
/* Find an entry in the third-level page table. */
#define pte_index(addr) (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))

@@ -450,6 +455,11 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)
return pud_val(pud) & PHYS_MASK & (s32)PAGE_MASK;
}

+static inline unsigned long pud_page_vaddr(pud_t pud)
+{
+ return (unsigned long) __va(pud_page_paddr(pud));
+}
+
/* Find an entry in the second-level page table. */
#define pmd_index(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))

@@ -502,6 +512,11 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
return pgd_val(pgd) & PHYS_MASK & (s32)PAGE_MASK;
}

+static inline unsigned long pgd_page_vaddr(pgd_t pgd)
+{
+ return (unsigned long) __va(pgd_page_paddr(pgd));
+}
+
/* Find an entry in the frst-level page table. */
#define pud_index(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 259bb6e..c12983b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -551,7 +551,6 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
unsigned long nr_pages = size >> PAGE_SHIFT;
unsigned long end_pfn = start_pfn + nr_pages;
unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
- unsigned long pfn;
int ret;

if (end_pfn > max_sparsemem_pfn) {
@@ -624,5 +623,34 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)

return ret;
}
-#endif

+#ifdef CONFIG_MEMORY_HOTREMOVE
+static void kernel_physical_mapping_remove(unsigned long start,
+ unsigned long end)
+{
+ start = (unsigned long)__va(start);
+ end = (unsigned long)__va(end);
+
+ remove_pagetable(start, end, true);
+
+}
+
+int arch_remove_memory(u64 start, u64 size)
+{
+ unsigned long start_pfn = start >> PAGE_SHIFT;
+ unsigned long nr_pages = size >> PAGE_SHIFT;
+ struct page *page = pfn_to_page(start_pfn);
+ struct zone *zone;
+ int ret = 0;
+
+ zone = page_zone(page);
+ ret = __remove_pages(zone, start_pfn, nr_pages);
+ WARN_ON_ONCE(ret);
+
+ kernel_physical_mapping_remove(start, start + size);
+
+ return ret;
+}
+
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+#endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8882187..e129d7c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1,4 +1,3 @@
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
/*
* Based on arch/arm/mm/mmu.c
*
@@ -24,6 +23,7 @@
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/libfdt.h>
+#include <linux/memremap.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
#include <linux/memblock.h>
@@ -119,7 +119,6 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
phys_addr_t pte_phys;
BUG_ON(!pgtable_alloc);
pte_phys = pgtable_alloc();
- pr_debug("Allocating PTE at %p\n", __va(pte_phys));
pte = pte_set_fixmap(pte_phys);
__pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
pte_clear_fixmap();
@@ -160,7 +159,6 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
phys_addr_t pmd_phys;
BUG_ON(!pgtable_alloc);
pmd_phys = pgtable_alloc();
- pr_debug("Allocating PMD at %p\n", __va(pmd_phys));
pmd = pmd_set_fixmap(pmd_phys);
__pud_populate(pud, pmd_phys, PUD_TYPE_TABLE);
pmd_clear_fixmap();
@@ -221,7 +219,6 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
phys_addr_t pud_phys;
BUG_ON(!pgtable_alloc);
pud_phys = pgtable_alloc();
- pr_debug("Allocating PUD at %p\n", __va(pud_phys));
__pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
}
BUG_ON(pgd_bad(*pgd));
@@ -546,7 +543,389 @@ void hotplug_paging(phys_addr_t start, phys_addr_t size)
__free_pages(pg, 0);
}

+#ifdef CONFIG_MEMORY_HOTREMOVE
+#define PAGE_INUSE 0xFD
+
+static void free_pagetable(struct page *page, int order, bool direct)
+{
+ unsigned long magic;
+ unsigned int nr_pages = 1 << order;
+ struct vmem_altmap *altmap = to_vmem_altmap((unsigned long) page);
+
+ if (altmap) {
+ vmem_altmap_free(altmap, nr_pages);
+ return;
+ }
+
+ /* bootmem page has reserved flag */
+ if (PageReserved(page)) {
+ __ClearPageReserved(page);
+
+ magic = (unsigned long)page->lru.next;
+ if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
+ while (nr_pages--)
+ put_page_bootmem(page++);
+ } else {
+ while (nr_pages--)
+ free_reserved_page(page++);
+ }
+ } else {
+ /*
+ * Only direct pagetable allocation (those allocated via
+ * hotplug) call the pgtable_page_ctor; vmemmap pgtable
+ * allocations don't.
+ */
+ if (direct)
+ pgtable_page_dtor(page);
+
+ free_pages((unsigned long)page_address(page), order);
+ }
+}
+
+static void free_pte_table(pmd_t *pmd, bool direct)
+{
+ pte_t *pte_start, *pte;
+ struct page *page;
+ int i;
+
+ pte_start = (pte_t *) pmd_page_vaddr(*pmd);
+ /* Check if there is no valid entry in the PMD */
+ for (i = 0; i < PTRS_PER_PTE; i++) {
+ pte = pte_start + i;
+ if (!pte_none(*pte))
+ return;
+ }
+
+ page = pmd_page(*pmd);
+
+ free_pagetable(page, 0, direct);
+
+ /*
+ * This spin lock could be only taken in _pte_aloc_kernel
+ * in mm/memory.c and nowhere else (for arm64). Not sure if
+ * the function above can be called concurrently. In doubt,
+ * I am living it here for now, but it probably can be removed
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pmd_clear(pmd);
+ spin_unlock(&init_mm.page_table_lock);
+}
+
+static void free_pmd_table(pud_t *pud, bool direct)
+{
+ pmd_t *pmd_start, *pmd;
+ struct page *page;
+ int i;
+
+ pmd_start = (pmd_t *) pud_page_vaddr(*pud);
+ /* Check if there is no valid entry in the PMD */
+ for (i = 0; i < PTRS_PER_PMD; i++) {
+ pmd = pmd_start + i;
+ if (!pmd_none(*pmd))
+ return;
+ }
+
+ page = pud_page(*pud);
+
+ free_pagetable(page, 0, direct);
+
+ /*
+ * This spin lock could be only taken in _pte_aloc_kernel
+ * in mm/memory.c and nowhere else (for arm64). Not sure if
+ * the function above can be called concurrently. In doubt,
+ * I am living it here for now, but it probably can be removed
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pud_clear(pud);
+ spin_unlock(&init_mm.page_table_lock);
+}
+
+/*
+ * When the PUD is folded on the PGD (three levels of paging),
+ * there's no need to free PUDs
+ */
+#if CONFIG_PGTABLE_LEVELS > 3
+static void free_pud_table(pgd_t *pgd, bool direct)
+{
+ pud_t *pud_start, *pud;
+ struct page *page;
+ int i;
+
+ pud_start = (pud_t *) pgd_page_vaddr(*pgd);
+ /* Check if there is no valid entry in the PUD */
+ for (i = 0; i < PTRS_PER_PUD; i++) {
+ pud = pud_start + i;
+ if (!pud_none(*pud))
+ return;
+ }
+
+ page = pgd_page(*pgd);
+
+ free_pagetable(page, 0, direct);
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pgd_clear(pgd);
+ spin_unlock(&init_mm.page_table_lock);
+}
+#endif
+
+static void remove_pte_table(pte_t *pte, unsigned long addr,
+ unsigned long end, bool direct)
+{
+ unsigned long next;
+ void *page_addr;
+
+ for (; addr < end; addr = next, pte++) {
+ next = (addr + PAGE_SIZE) & PAGE_MASK;
+ if (next > end)
+ next = end;
+
+ if (!pte_present(*pte))
+ continue;
+
+ if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) {
+ /*
+ * Do not free direct mapping pages since they were
+ * freed when offlining, or simplely not in use.
+ */
+ if (!direct)
+ free_pagetable(pte_page(*pte), 0, direct);
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pte_clear(&init_mm, addr, pte);
+ spin_unlock(&init_mm.page_table_lock);
+ } else {
+ /*
+ * If we are here, we are freeing vmemmap pages since
+ * direct mapped memory ranges to be freed are aligned.
+ *
+ * If we are not removing the whole page, it means
+ * other page structs in this page are being used and
+ * we canot remove them. So fill the unused page_structs
+ * with 0xFD, and remove the page when it is wholly
+ * filled with 0xFD.
+ */
+ memset((void *)addr, PAGE_INUSE, next - addr);
+
+ page_addr = page_address(pte_page(*pte));
+ if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
+ free_pagetable(pte_page(*pte), 0, direct);
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pte_clear(&init_mm, addr, pte);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+ }
+ }
+
+ // I am adding this flush here in simmetry to the x86 code.
+ // Why do I need to call it here and not in remove_p[mu]d
+ flush_tlb_all();
+}
+
+static void remove_pmd_table(pmd_t *pmd, unsigned long addr,
+ unsigned long end, bool direct)
+{
+ unsigned long next;
+ void *page_addr;
+ pte_t *pte;
+
+ for (; addr < end; addr = next, pmd++) {
+ next = pmd_addr_end(addr, end);
+
+ if (!pmd_present(*pmd))
+ continue;
+
+ // check if we are using 2MB section mappings
+ if (pmd_sect(*pmd)) {
+ if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) {
+ if (!direct) {
+ free_pagetable(pmd_page(*pmd),
+ get_order(PMD_SIZE), direct);
+ }
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pmd_clear(pmd);
+ spin_unlock(&init_mm.page_table_lock);
+ } else {
+ /* If here, we are freeing vmemmap pages. */
+ memset((void *)addr, PAGE_INUSE, next - addr);
+
+ page_addr = page_address(pmd_page(*pmd));
+ if (!memchr_inv(page_addr, PAGE_INUSE,
+ PMD_SIZE)) {
+ free_pagetable(pmd_page(*pmd),
+ get_order(PMD_SIZE), direct);
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pmd_clear(pmd);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+ }
+ continue;
+ }
+
+ BUG_ON(!pmd_table(*pmd));
+
+ pte = pte_offset_map(pmd, addr);
+ remove_pte_table(pte, addr, next, direct);
+ free_pte_table(pmd, direct);
+ }
+}
+
+static void remove_pud_table(pud_t *pud, unsigned long addr,
+ unsigned long end, bool direct)
+{
+ unsigned long next;
+ pmd_t *pmd;
+ void *page_addr;
+
+ for (; addr < end; addr = next, pud++) {
+ next = pud_addr_end(addr, end);
+ if (!pud_present(*pud))
+ continue;
+ /*
+ * If we are using 4K granules, check if we are using
+ * 1GB section mapping.
+ */
+ if (pud_sect(*pud)) {
+ if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) {
+ if (!direct) {
+ free_pagetable(pud_page(*pud),
+ get_order(PUD_SIZE), direct);
+ }
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pud_clear(pud);
+ spin_unlock(&init_mm.page_table_lock);
+ } else {
+ /* If here, we are freeing vmemmap pages. */
+ memset((void *)addr, PAGE_INUSE, next - addr);
+
+ page_addr = page_address(pud_page(*pud));
+ if (!memchr_inv(page_addr, PAGE_INUSE,
+ PUD_SIZE)) {
+
+ free_pagetable(pud_page(*pud),
+ get_order(PUD_SIZE), direct);
+
+ /*
+ * This spin lock could be only
+ * taken in _pte_aloc_kernel in
+ * mm/memory.c and nowhere else
+ * (for arm64). Not sure if the
+ * function above can be called
+ * concurrently. In doubt,
+ * I am living it here for now,
+ * but it probably can be removed.
+ */
+ spin_lock(&init_mm.page_table_lock);
+ pud_clear(pud);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+ }
+ continue;
+ }
+
+ BUG_ON(!pud_table(*pud));
+
+ pmd = pmd_offset(pud, addr);
+ remove_pmd_table(pmd, addr, next, direct);
+ free_pmd_table(pud, direct);
+ }
+}
+
+void remove_pagetable(unsigned long start, unsigned long end, bool direct)
+{
+ unsigned long next;
+ unsigned long addr;
+ pgd_t *pgd;
+ pud_t *pud;
+
+ for (addr = start; addr < end; addr = next) {
+ next = pgd_addr_end(addr, end);
+
+ pgd = pgd_offset_k(addr);
+ if (pgd_none(*pgd))
+ continue;
+
+ pud = pud_offset(pgd, addr);
+ remove_pud_table(pud, addr, next, direct);
+ /*
+ * When the PUD is folded on the PGD (three levels of paging),
+ * I did already clear the PMD page in free_pmd_table,
+ * and reset the corresponding PGD==PUD entry.
+ */
+#if CONFIG_PGTABLE_LEVELS > 3
+ free_pud_table(pgd, direct);
#endif
+ }
+
+ flush_tlb_all();
+}
+
+
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+#endif /* CONFIG_MEMORY_HOTPLUG */

/*
* Check whether a kernel address is valid (derived from arch/x86/).
@@ -629,6 +1008,9 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
#endif /* CONFIG_ARM64_64K_PAGES */
void vmemmap_free(unsigned long start, unsigned long end)
{
+#ifdef CONFIG_MEMORY_HOTREMOVE
+ remove_pagetable(start, end, false);
+#endif
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

--
1.9.1