diff options
| author | Janosch Frank <frankja@linux.vnet.ibm.com> | 2017-03-02 15:23:42 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-18 19:09:58 +0800 |
| commit | b0e85701a7766341618d5e924f29f359431f9c91 (patch) | |
| tree | 8f334619f8ac8c55915f63d809e59a594b098b81 | |
| parent | 61fbad6a28fd3c80567cc615e2de6bd6476ab60c (diff) | |
KVM: s390: Fix guest migration for huge guests resulting in panic
commit 2e4d88009f57057df7672fa69a32b5224af54d37 upstream.
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: <stable@vger.kernel.org> # 3.16+
Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/s390/mm/pgtable.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 8345ae1f117d..05ae254f84cf 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -1237,11 +1237,28 @@ EXPORT_SYMBOL_GPL(s390_reset_cmma); */ bool gmap_test_and_clear_dirty(unsigned long address, struct gmap *gmap) { + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; pte_t *pte; spinlock_t *ptl; bool dirty = false; - pte = get_locked_pte(gmap->mm, address, &ptl); + pgd = pgd_offset(gmap->mm, address); + pud = pud_alloc(gmap->mm, pgd, address); + if (!pud) + return false; + pmd = pmd_alloc(gmap->mm, pud, address); + 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; + + pte = pte_alloc_map_lock(gmap->mm, pmd, address, &ptl); if (unlikely(!pte)) return false; |