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virtio-ccw: feature bits > 31 handling 

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 <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Cornelia Huck 2015-09-11 15:16:43 +02:00 committed by Michael S. Tsirkin
parent 79cd0c80f8
commit b4f8f9df15
1 changed files with 8 additions and 13 deletions
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21
hw/s390x/virtio-ccw.c
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@ -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));