From: Janosch Frank Date: Thu, 2 Mar 2017 14:23:42 +0000 (+0100) Subject: KVM: s390: Fix guest migration for huge guests resulting in panic X-Git-Tag: v5.15~11685^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2e4d88009f57057df7672fa69a32b5224af54d37;p=platform%2Fkernel%2Flinux-starfive.git KVM: s390: Fix guest migration for huge guests resulting in panic While we can technically not run huge page guests right now, we can setup a guest with huge pages. Trying to migrate it will trigger a VM_BUG_ON and, if the kernel is not configured to panic on a BUG, it will happily try to work on non-existing page table entries. With this patch, we always return "dirty" if we encounter a large page when migrating. This at least fixes the immediate problem until we have proper handling for both kind of pages. Fixes: 15f36eb ("KVM: s390: Add proper dirty bitmap support to S390 kvm.") Cc: # 3.16+ Signed-off-by: Janosch Frank Acked-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky --- diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index b48dc5f..463e5ef 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -608,12 +608,29 @@ void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep) bool test_and_clear_guest_dirty(struct mm_struct *mm, unsigned long addr) { spinlock_t *ptl; + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; pgste_t pgste; pte_t *ptep; pte_t pte; 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)) return false;