KVM: s390: vsie: Fix nested guest memory shadowing

Fix _do_shadow_pte() to use the correct pointer (guest pte instead of
nested guest) to set up the new pte.

Add a check to return -EOPNOTSUPP if the mapping for the nested guest
is writeable but the same page in the guest is only read-only.

Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 8fd690255e1b14dbc3e2b90dda70a45f85a02ca9..6bc30f67892151752dab48008227c282deb87534 100644 (file)
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1436,13 +1436,19 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union
 
        if (!pgste_get_trylock(ptep_h, &pgste))
                return -EAGAIN;
-       newpte = _pte(f->pfn, f->writable, !p, 0);
-       newpte.s.d |= ptep->s.d;
-       newpte.s.sd |= ptep->s.sd;
-       newpte.h.p &= ptep->h.p;
-       pgste = _gmap_ptep_xchg(sg->parent, ptep_h, newpte, pgste, f->gfn, false);
-       pgste.vsie_notif = 1;
+       newpte = _pte(f->pfn, f->writable, !p, ptep_h->s.s);
+       newpte.s.d |= ptep_h->s.d;
+       newpte.s.sd |= ptep_h->s.sd;
+       newpte.h.p &= ptep_h->h.p;
+       if (!newpte.h.p && !f->writable) {
+               rc = -EOPNOTSUPP;
+       } else {
+               pgste = _gmap_ptep_xchg(sg->parent, ptep_h, newpte, pgste, f->gfn, false);
+               pgste.vsie_notif = 1;
+       }
        pgste_set_unlock(ptep_h, pgste);
+       if (rc)
+               return rc;
 
        newpte = _pte(f->pfn, 0, !p, 0);
        if (!pgste_get_trylock(ptep, &pgste))
@@ -1477,6 +1483,9 @@ static int _do_shadow_crste(struct gmap *sg, gpa_t raddr, union crste *host, uni
                newcrste.h.p &= oldcrste.h.p;
                newcrste.s.fc1.vsie_notif = 1;
                newcrste.s.fc1.prefix_notif = oldcrste.s.fc1.prefix_notif;
+               newcrste.s.fc1.s = oldcrste.s.fc1.s;
+               if (!newcrste.h.p && !f->writable)
+                       return -EOPNOTSUPP;
        } while (!_gmap_crstep_xchg_atomic(sg->parent, host, oldcrste, newcrste, f->gfn, false));
 
        newcrste = _crste_fc1(f->pfn, oldcrste.h.tt, 0, !p);