mm: introduce ctor/dtor at PGD level

Following on from the introduction of P4D-level ctor/dtor, let's finish
the job and introduce ctor/dtor at PGD level.  The incurred improvement in
page accounting is minimal - the main motivation is to create a single,
generic place where construction/destruction hooks can be added for all
page table pages.

This patch should cover all architectures and all configurations where
PGDs are one or more regular pages.  This excludes any configuration where
PGDs are allocated from a kmem_cache object.

Link: https://lkml.kernel.org/r/20250103184415.2744423-7-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index 5fced6d3c36b..b19b6ed2ab53 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -130,11 +130,18 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
 
 static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 {
-	return (pgd_t *) crst_table_alloc(mm);
+	unsigned long *table = crst_table_alloc(mm);
+
+	if (!table)
+		return NULL;
+	pagetable_pgd_ctor(virt_to_ptdesc(table));
+
+	return (pgd_t *) table;
 }
 
 static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 {
+	pagetable_dtor(virt_to_ptdesc(pgd));
 	crst_table_free(mm, (unsigned long *) pgd);
 }