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* Fix freeing of PMD-sized vmemmap pages

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* Update comment about pgd_list
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Merge tag 'x86_mm_for_7.2-rc1' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip

Pull x86 mm updates from Dave Hansen:
 "There's a small comment fixup, followed by an actual bug fix. The bug
  fix is slightly new territory for us. It fixes a real regression, but
  it is from ~6.18 not a _new_ regression. It was mostly only biting
  folks doing hotplug memory testing. So, it was queued in here and held
  for the merge window instead of going via x86/urgent.

   - Fix freeing of PMD-sized vmemmap pages

   - Update comment about pgd_list"

* tag 'x86_mm_for_7.2-rc1' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Fix freeing of PMD-sized vmemmap pages
  x86: Update comment about pgd_list
This commit is contained in:
Linus Torvalds 2026-06-16 06:17:23 +05:30
commit 7d36844ae7
3 changed files with 31 additions and 25 deletions
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5
arch/x86/mm/fault.c
View File

@ -169,6 +169,11 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
}
DEFINE_SPINLOCK(pgd_lock);
/*
* List of all process' PGD pages (excluding init_mm and some other special
* system-wide PGDs). Mainly used to keep the kernel portion of the address
* space in sync across mms.
*/
LIST_HEAD(pgd_list);
#ifdef CONFIG_X86_32

40
arch/x86/mm/init_64.c
View File

@ -1014,7 +1014,7 @@ static void __meminit free_pagetable(struct page *page, int order)
#ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
enum bootmem_type type = bootmem_type(page);
if (type == SECTION_INFO || type == MIX_SECTION_INFO) {
if (type == MIX_SECTION_INFO) {
while (nr_pages--)
put_page_bootmem(page++);
} else {
@ -1028,13 +1028,24 @@ static void __meminit free_pagetable(struct page *page, int order)
}
}
static void __meminit free_hugepage_table(struct page *page,
static void __meminit free_vmemmap_pages(struct page *page, unsigned int order,
struct vmem_altmap *altmap)
{
if (altmap)
vmem_altmap_free(altmap, PMD_SIZE / PAGE_SIZE);
else
free_pagetable(page, get_order(PMD_SIZE));
unsigned long nr_pages = 1u << order;
if (altmap) {
vmem_altmap_free(altmap, nr_pages);
} else if (PageReserved(page)) {
if (IS_ENABLED(CONFIG_HAVE_BOOTMEM_INFO_NODE) &&
bootmem_type(page) == SECTION_INFO) {
while (nr_pages--)
put_page_bootmem(page++);
} else {
free_reserved_pages(page, nr_pages);
}
} else {
__free_pages(page, order);
}
}
static void __meminit free_pte_table(pte_t *pte_start, pmd_t *pmd)
@ -1118,7 +1129,8 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
return;
if (!direct)
free_pagetable(pte_page(*pte), 0);
/* We never populate base pages from the altmap. */
free_vmemmap_pages(pte_page(*pte), 0, NULL);
spin_lock(&init_mm.page_table_lock);
pte_clear(&init_mm, addr, pte);
@ -1153,19 +1165,19 @@ remove_pmd_table(pmd_t *pmd_start, unsigned long addr, unsigned long end,
if (IS_ALIGNED(addr, PMD_SIZE) &&
IS_ALIGNED(next, PMD_SIZE)) {
if (!direct)
free_hugepage_table(pmd_page(*pmd),
altmap);
free_vmemmap_pages(pmd_page(*pmd),
PMD_ORDER, altmap);
spin_lock(&init_mm.page_table_lock);
pmd_clear(pmd);
spin_unlock(&init_mm.page_table_lock);
pages++;
} else if (vmemmap_pmd_is_unused(addr, next)) {
free_hugepage_table(pmd_page(*pmd),
altmap);
spin_lock(&init_mm.page_table_lock);
pmd_clear(pmd);
spin_unlock(&init_mm.page_table_lock);
free_vmemmap_pages(pmd_page(*pmd), PMD_ORDER,
altmap);
spin_lock(&init_mm.page_table_lock);
pmd_clear(pmd);
spin_unlock(&init_mm.page_table_lock);
}
continue;
}

11
arch/x86/mm/pgtable.c
View File

@ -99,17 +99,6 @@ static void pgd_dtor(pgd_t *pgd)
spin_unlock(&pgd_lock);
}
/*
* List of all pgd's needed for non-PAE so it can invalidate entries
* in both cached and uncached pgd's; not needed for PAE since the
* kernel pmd is shared. If PAE were not to share the pmd a similar
* tactic would be needed. This is essentially codepath-based locking
* against pageattr.c; it is the unique case in which a valid change
* of kernel pagetables can't be lazily synchronized by vmalloc faults.
* vmalloc faults work because attached pagetables are never freed.
* -- nyc
*/
#ifdef CONFIG_X86_PAE
/*
* In PAE mode, we need to do a cr3 reload (=tlb flush) when