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Subject[PATCH] x86/mm: synchronize pgd in vmemmap_free()
Date
When we free kernel virtual map we should synchronize p4d/pud for
all the pgds to avoid any stall entry in non canonical pgd.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@suse.de>
---
arch/x86/mm/init_64.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ff95fe8..df753f8 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -108,8 +108,6 @@ void sync_global_pgds(unsigned long start, unsigned long end)
BUILD_BUG_ON(pgd_none(*pgd_ref));
p4d_ref = p4d_offset(pgd_ref, address);

- if (p4d_none(*p4d_ref))
- continue;

spin_lock(&pgd_lock);
list_for_each_entry(page, &pgd_list, lru) {
@@ -123,12 +121,16 @@ void sync_global_pgds(unsigned long start, unsigned long end)
pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
spin_lock(pgt_lock);

- if (!p4d_none(*p4d_ref) && !p4d_none(*p4d))
- BUG_ON(p4d_page_vaddr(*p4d)
- != p4d_page_vaddr(*p4d_ref));
-
- if (p4d_none(*p4d))
+ if (p4d_none(*p4d_ref)) {
set_p4d(p4d, *p4d_ref);
+ } else {
+ if (!p4d_none(*p4d_ref) && !p4d_none(*p4d))
+ BUG_ON(p4d_page_vaddr(*p4d)
+ != p4d_page_vaddr(*p4d_ref));
+
+ if (p4d_none(*p4d))
+ set_p4d(p4d, *p4d_ref);
+ }

spin_unlock(pgt_lock);
}
@@ -1024,6 +1026,7 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct)
void __ref vmemmap_free(unsigned long start, unsigned long end)
{
remove_pagetable(start, end, false);
+ sync_global_pgds(start, end - 1);
}

#ifdef CONFIG_MEMORY_HOTREMOVE
--
2.4.11
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