KVM: s390: Fix guest migration for huge guests resulting in panic

bool test_and_clear_guest_dirty(struct mm_struct *mm, unsigned long addr)

bool test_and_clear_guest_dirty(struct mm_struct *mm, unsigned long addr)

{

{

	spinlock_t *ptl;

	spinlock_t *ptl;

	pgd_t *pgd;

	pud_t *pud;

	pmd_t *pmd;

	pgste_t pgste;

	pgste_t pgste;

	pte_t *ptep;

	pte_t *ptep;

	pte_t pte;

	pte_t pte;

	bool dirty;

	bool dirty;

	ptep = get_locked_pte(mm, addr, &ptl);

	pgd = pgd_offset(mm, addr);

	pud = pud_alloc(mm, pgd, addr);

	if (!pud)

		return false;

	pmd = pmd_alloc(mm, pud, addr);

	if (!pmd)

		return false;

	/* We can't run guests backed by huge pages, but userspace can

	 * still set them up and then try to migrate them without any

	 * migration support.

	 */

	if (pmd_large(*pmd))

		return true;

	ptep = pte_alloc_map_lock(mm, pmd, addr, &ptl);

	if (unlikely(!ptep))

	if (unlikely(!ptep))

		return false;

		return false;