From: Cornelia Huck <cornelia.h...@de.ibm.com>
We currently switch off the VERSION_1 feature bit if the guest has
not negotiated at least revision 1. As no feature bits beyond 31 are
valid however unless VERSION_1 has been negotiated, make sure that
legacy guests never see a feature bit beyond 31.
Reviewed-by: David Hildenbrand <d...@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.h...@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
hw/s390x/virtio-ccw.c | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 85e2a5d..eed7b3e 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -468,15 +468,12 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
NULL);
if (features.index == 0) {
features.features = (uint32_t)vdev->host_features;
- } else if (features.index == 1) {
- features.features = (uint32_t)(vdev->host_features >> 32);
+ } else if ((features.index == 1) && (dev->revision >= 1)) {
/*
- * Don't offer version 1 to the guest if it did not
- * negotiate at least revision 1.
+ * Only offer feature bits beyond 31 if the guest has
+ * negotiated at least revision 1.
*/
- if (dev->revision <= 0) {
- features.features &= ~(1 << (VIRTIO_F_VERSION_1 - 32));
- }
+ features.features = (uint32_t)(vdev->host_features >> 32);
} else {
/* Return zeroes if the guest supports more feature bits. */
features.features = 0;
@@ -515,14 +512,12 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
virtio_set_features(vdev,
(vdev->guest_features &
0xffffffff00000000ULL) |
features.features);
- } else if (features.index == 1) {
+ } else if ((features.index == 1) && (dev->revision >= 1)) {
/*
- * The guest should not set version 1 if it didn't
- * negotiate a revision >= 1.
+ * If the guest did not negotiate at least revision 1,
+ * we did not offer it any feature bits beyond 31. Such a
+ * guest passing us any bit here is therefore buggy.
*/
- if (dev->revision <= 0) {
- features.features &= ~(1 << (VIRTIO_F_VERSION_1 - 32));
- }
virtio_set_features(vdev,
(vdev->guest_features &
0x00000000ffffffffULL) |
((uint64_t)features.features << 32));
--
MST
