On Tue, Mar 31, 2009 at 5:28 PM, Dustin Kirkland <kirkland@xxxxxxxxxxxxx> wrote: > I'm receiving a heavy volume of Ubuntu Jaunty Beta users reporting > that Jaunty hosts running kvm-84 (userspace and kernel) are not able > to boot previously-working Hardy guests (2.6.24 kernel) if virtio > networking is enabled [1]. Users report that if e1000 is used > instead, the guest is able to boot (with degraded network performance, > obviously). Users are also reporting that this was not a problem when > kvm-82 was used in Jaunty (though we also merged libvirt 0.5.1 up to > 0.6.0 in roughly the same timeframe). ... > [1] https://bugs.launchpad.net/ubuntu/+source/kvm/+bug/331128 Howdy- Just a follow-up... Anthony was able to confirm this issue, and create a patch for KVM, which we're carrying in Ubuntu. It's a bit of a special-case hack, but I'm dropping it here for the sake of completeness. Basically, Hardy guests do not have working GSO (general segment offload) support. Some changes in kvm/libvirt appear to be exposing this, and breaking some guests when running virtio. This patch from Anthony basically disables this support in KVM userspace (until we have a better solution for auto-detecting GSO support or lack thereof). :-Dustin Work around broken virtio drivers in 2.6.26 Signed-off-by: Anthony Liguori <aliguori@xxxxxxxxxx> diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c index 9bce3a0..5b615f9 100644 --- a/qemu/hw/virtio-net.c +++ b/qemu/hw/virtio-net.c @@ -120,6 +120,9 @@ static uint32_t virtio_net_get_features(VirtIODevice *vdev) if (tap_has_vnet_hdr(host)) { tap_using_vnet_hdr(host, 1); +#if 0 + /* Stop advertising advanced features until we work around the fact + * that this is totally broken in 2.6.26 kernels */ features |= (1 << VIRTIO_NET_F_CSUM); features |= (1 << VIRTIO_NET_F_GUEST_CSUM); features |= (1 << VIRTIO_NET_F_GUEST_TSO4); @@ -130,6 +133,7 @@ static uint32_t virtio_net_get_features(VirtIODevice *vdev) features |= (1 << VIRTIO_NET_F_HOST_ECN); features |= (1 << VIRTIO_NET_F_MRG_RXBUF); /* Kernel can't actually handle UFO in software currently. */ +#endif } #endif @@ -374,8 +378,14 @@ static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt, struct virtio_net_hdr *hdr = iov[0].iov_base; int offset = 0; +#if 0 hdr->flags = 0; hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; +#else + /* we need to clear out the whole header, including any garbage that may be + */ + memset(hdr, 0, sizeof(*hdr)); +#endif #ifdef TAP_VNET_HDR if (tap_has_vnet_hdr(n->vc->vlan->first_client)) { -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
