[PATCH 4/8] x86/mm: Add sync_global_pgds() for configuration with 5-level paging

[Kirill A. Shutemov]

This basically restores slightly modified version of original
sync_global_pgds() which we had before folded p4d was introduced.

The only modification is protection against 'address' overflow.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
 arch/x86/mm/init_64.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a242139df8fe..0b62b13e8655 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -92,6 +92,40 @@ __setup("noexec32=", nonx32_setup);
  * When memory was added make sure all the processes MM have
  * suitable PGD entries in the local PGD level page.
  */
+#ifdef CONFIG_X86_5LEVEL
+void sync_global_pgds(unsigned long start, unsigned long end)
+{
+       unsigned long address;
+
+       for (address = start; address <= end && address >= start; address += 
PGDIR_SIZE) {
+               const pgd_t *pgd_ref = pgd_offset_k(address);
+               struct page *page;
+
+               if (pgd_none(*pgd_ref))
+                       continue;
+
+               spin_lock(&pgd_lock);
+               list_for_each_entry(page, &pgd_list, lru) {
+                       pgd_t *pgd;
+                       spinlock_t *pgt_lock;
+
+                       pgd = (pgd_t *)page_address(page) + pgd_index(address);
+                       /* the pgt_lock only for Xen */
+                       pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
+                       spin_lock(pgt_lock);
+
+                       if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
+                               BUG_ON(pgd_page_vaddr(*pgd) != 
pgd_page_vaddr(*pgd_ref));
+
+                       if (pgd_none(*pgd))
+                               set_pgd(pgd, *pgd_ref);
+
+                       spin_unlock(pgt_lock);
+               }
+               spin_unlock(&pgd_lock);
+       }
+}
+#else
 void sync_global_pgds(unsigned long start, unsigned long end)
 {
        unsigned long address;
@@ -135,6 +169,7 @@ void sync_global_pgds(unsigned long start, unsigned long 
end)
                spin_unlock(&pgd_lock);
        }
 }
+#endif
 
 /*
  * NOTE: This function is marked __ref because it calls __init function
-- 
2.11.0