Merge tag 'powerpc-5.2-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:
 "One fix for a regression introduced by our 32-bit KASAN support, which
  broke booting on machines with "bootx" early debugging enabled.

  A fix for a bug which broke kexec on 32-bit, introduced by changes to
  the 32-bit STRICT_KERNEL_RWX support in v5.1.

  Finally two fixes going to stable for our THP split/collapse handling,
  discovered by Nick. The first fixes random crashes and/or corruption
  in guests under sufficient load.

  Thanks to: Nicholas Piggin, Christophe Leroy, Aaro Koskinen, Mathieu
  Malaterre"

* tag 'powerpc-5.2-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/32s: fix booting with CONFIG_PPC_EARLY_DEBUG_BOOTX
  powerpc/64s: __find_linux_pte() synchronization vs pmdp_invalidate()
  powerpc/64s: Fix THP PMD collapse serialisation
  powerpc: Fix kexec failure on book3s/32

2 files changed, 17 insertions, 2 deletions

diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index a255707e4aee..01bc9663360d 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -112,6 +112,9 @@ pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 	/*
 	 * This ensures that generic code that rely on IRQ disabling
 	 * to prevent a parallel THP split work as expected.
+	 *
+	 * Marking the entry with _PAGE_INVALID && ~_PAGE_PRESENT requires
+	 * a special case check in pmd_access_permitted.
 	 */
 	serialize_against_pte_lookup(vma->vm_mm);
 	return __pmd(old_pmd);
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 39d2f8012386..fc10c0c24f51 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -368,13 +368,25 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
 	pdshift = PMD_SHIFT;
 	pmdp = pmd_offset(&pud, ea);
 	pmd  = READ_ONCE(*pmdp);
+
 	/*
-	 * A hugepage collapse is captured by pmd_none, because
-	 * it mark the pmd none and do a hpte invalidate.
+	 * A hugepage collapse is captured by this condition, see
+	 * pmdp_collapse_flush.
 	 */
 	if (pmd_none(pmd))
 		return NULL;
 
+#ifdef CONFIG_PPC_BOOK3S_64
+	/*
+	 * A hugepage split is captured by this condition, see
+	 * pmdp_invalidate.
+	 *
+	 * Huge page modification can be caught here too.
+	 */
+	if (pmd_is_serializing(pmd))
+		return NULL;
+#endif
+
 	if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) {
 		if (is_thp)
 			*is_thp = true;