> 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. > > Signed-off-by: Cornelia Huck <cornelia.h...@de.ibm.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));
Looks sane to me! Reviewed-by: David Hildenbrand <d...@linux.vnet.ibm.com> David