When shadowing a nested guest, a check is performed and no shadowing is
attempted if the nested guest is already shadowed.

The existing check was incomplete; fix it by also checking whether the
leaf DAT table entry in the existing shadow gmap has the same protection
as the one specified in the guest DAT entry.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
---
 arch/s390/kvm/gaccess.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index e490ae87db44..f5ffb11c8ef9 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1505,7 +1505,8 @@ static int _gaccess_do_shadow(struct kvm_s390_mmu_cache *mc, struct gmap *sg,
 		return rc;
 
 	/* A race occourred. The shadow mapping is already valid, nothing to do */
-	if ((ptep && !ptep->h.i) || (!ptep && crste_leaf(*table)))
+	if ((ptep && !ptep->h.i && ptep->h.p == w->p) ||
+	    (!ptep && crste_leaf(*table) && !table->h.i && table->h.p == w->p))
 		return 0;
 
 	gl = get_level(table, ptep);
-- 
2.53.0