[PATCH] x86/mm: Initialize pgd cache during mm initialization

[Nadav Amit <nadav.amit@gmail.com>]

Poking-mm initialization might require to duplicate the PGD in early
stage. Initialize the PGD cache earlier to prevent boot failures.

Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 4fc19708b165 ("x86/alternatives: Initialize temporary mm for patching")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 arch/x86/include/asm/pgtable.h |  1 +
 arch/x86/mm/pgtable.c          | 10 ++++++----
 init/main.c                    |  1 +
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 6b6bfdfe83aa..9635662e1163 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1027,6 +1027,7 @@ static inline int pgd_none(pgd_t pgd)
 
 extern int direct_gbpages;
 void init_mem_mapping(void);
+void pgd_cache_init(void);
 void early_alloc_pgt_buf(void);
 extern void memblock_find_dma_reserve(void);
 
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 3dbf440d4114..1f67b1e15bf6 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -373,14 +373,14 @@ static void pgd_prepopulate_user_pmd(struct mm_struct *mm,
 
 static struct kmem_cache *pgd_cache;
 
-static int __init pgd_cache_init(void)
+void __init pgd_cache_init(void)
 {
 	/*
 	 * When PAE kernel is running as a Xen domain, it does not use
 	 * shared kernel pmd. And this requires a whole page for pgd.
 	 */
 	if (!SHARED_KERNEL_PMD)
-		return 0;
+		return;
 
 	/*
 	 * when PAE kernel is not running as a Xen domain, it uses
@@ -390,9 +390,7 @@ static int __init pgd_cache_init(void)
 	 */
 	pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
 				      SLAB_PANIC, NULL);
-	return 0;
 }
-core_initcall(pgd_cache_init);
 
 static inline pgd_t *_pgd_alloc(void)
 {
@@ -420,6 +418,10 @@ static inline void _pgd_free(pgd_t *pgd)
 }
 #else
 
+void __init pgd_cache_init(void)
+{
+}
+
 static inline pgd_t *_pgd_alloc(void)
 {
 	return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER);
diff --git a/init/main.c b/init/main.c
index 949eed8015ec..7fac4ac2fede 100644
--- a/init/main.c
+++ b/init/main.c
@@ -537,6 +537,7 @@ static void __init mm_init(void)
 	init_espfix_bsp();
 	/* Should be run after espfix64 is set up. */
 	pti_init();
+	pgd_cache_init();
 }
 
 void __init __weak arch_call_rest_init(void)
-- 
2.17.1