Michael S. Tsirkin
2019-Dec-23 19:44 UTC
[PATCH net] virtio_net: CTRL_GUEST_OFFLOADS depends on CTRL_VQ
On Mon, Dec 23, 2019 at 09:40:11AM -0800, Alistair Delva wrote:> Hi Michael, > > On Mon, Dec 23, 2019 at 6:09 AM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > The only way for guest to control offloads (as enabled by > > VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) is by sending commands > > through CTRL_VQ. So it does not make sense to > > acknowledge VIRTIO_NET_F_CTRL_GUEST_OFFLOADS without > > VIRTIO_NET_F_CTRL_VQ. > > > > The spec does not outlaw devices with such a configuration, > > but Linux assumed that with VIRTIO_NET_F_CTRL_GUEST_OFFLOADS > > control vq is always there, resulting in the following crash > > when configuring LRO: > > > > kernel BUG at drivers/net/virtio_net.c:1591! > > invalid opcode: 0000 [#1] PREEMPT SMP PTI > > CPU: 1 PID: 483 Comm: Binder:330_1 Not tainted 5.4.5-01326-g19463e9acaac #1 > > Hardware name: ChromiumOS crosvm, BIOS 0 > > RIP: 0010:virtnet_send_command+0x15d/0x170 [virtio_net] > > Code: d8 00 00 00 80 78 02 00 0f 94 c0 65 48 8b 0c 25 28 00 00 00 48 3b 4c 24 70 75 11 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d > > +c3 <0f> 0b e8 ec a4 12 c8 66 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 > > RSP: 0018:ffffb97940e7bb50 EFLAGS: 00010246 > > RAX: ffffffffc0596020 RBX: ffffa0e1fc8ea840 RCX: 0000000000000017 > > RDX: ffffffffc0596110 RSI: 0000000000000011 RDI: 000000000000000d > > RBP: ffffb97940e7bbf8 R08: ffffa0e1fc8ea0b0 R09: ffffa0e1fc8ea0b0 > > R10: ffffffffffffffff R11: ffffffffc0590940 R12: 0000000000000005 > > R13: ffffa0e1ffad2c00 R14: ffffb97940e7bc08 R15: 0000000000000000 > > FS: 0000000000000000(0000) GS:ffffa0e1fd100000(006b) knlGS:00000000e5ef7494 > > CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 > > CR2: 00000000e5eeb82c CR3: 0000000079b06001 CR4: 0000000000360ee0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > ? preempt_count_add+0x58/0xb0 > > ? _raw_spin_lock_irqsave+0x36/0x70 > > ? _raw_spin_unlock_irqrestore+0x1a/0x40 > > ? __wake_up+0x70/0x190 > > virtnet_set_features+0x90/0xf0 [virtio_net] > > __netdev_update_features+0x271/0x980 > > ? nlmsg_notify+0x5b/0xa0 > > dev_disable_lro+0x2b/0x190 > > ? inet_netconf_notify_devconf+0xe2/0x120 > > devinet_sysctl_forward+0x176/0x1e0 > > proc_sys_call_handler+0x1f0/0x250 > > proc_sys_write+0xf/0x20 > > __vfs_write+0x3e/0x190 > > ? __sb_start_write+0x6d/0xd0 > > vfs_write+0xd3/0x190 > > ksys_write+0x68/0xd0 > > __ia32_sys_write+0x14/0x20 > > do_fast_syscall_32+0x86/0xe0 > > entry_SYSENTER_compat+0x7c/0x8e > > > > A similar crash will likely trigger when enabling XDP. > > > > Reported-by: Alistair Delva <adelva at google.com> > > Reported-by: Willem de Bruijn <willemdebruijn.kernel at gmail.com> > > Fixes: 3f93522ffab2 ("virtio-net: switch off offloads on demand if possible on XDP set") > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > --- > > > > Lightly tested. > > > > Alistair, could you please test and confirm that this resolves the > > crash for you? > > This patch doesn't work. The reason is that NETIF_F_LRO is also turned > on by TSO4/TSO6, which your patch didn't check for. So it ends up > going through the same path and crashing in the same way. > > if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) || > virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6)) > dev->features |= NETIF_F_LRO; > > It sounds like this patch is fixing something slightly differently to > my patch fixed. virtnet_set_features() doesn't care about > GUEST_OFFLOADS, it only tests against NETIF_F_LRO. Even if "offloads" > is zero, it will call virtnet_set_guest_offloads(), which triggers the > crash.Oh wait a second. You mean when we try to clear the offloads, right?> So either we need to ensure NETIF_F_LRO is never set, or > virtnet_set_features needs to be updated to check for GUEST_OFFLOADS, > right?So we have: static int virtnet_set_features(struct net_device *dev, netdev_features_t features) { struct virtnet_info *vi = netdev_priv(dev); u64 offloads; int err; if ((dev->features ^ features) & NETIF_F_LRO) { if (vi->xdp_queue_pairs) return -EBUSY; if (features & NETIF_F_LRO) offloads = vi->guest_offloads_capable; else offloads = 0; err = virtnet_set_guest_offloads(vi, offloads); if (err) return err; vi->guest_offloads = offloads; } return 0; } and static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64 offloads) { struct scatterlist sg; vi->ctrl->offloads = cpu_to_virtio64(vi->vdev, offloads); sg_init_one(&sg, &vi->ctrl->offloads, sizeof(vi->ctrl->offloads)); if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_GUEST_OFFLOADS, VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, &sg)) { dev_warn(&vi->dev->dev, "Fail to set guest offload.\n"); return -EINVAL; } return 0; } finally static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd, struct scatterlist *out) { struct scatterlist *sgs[4], hdr, stat; unsigned out_num = 0, tmp; /* Caller should know better */ BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)); vi->ctrl->status = ~0; ... } so return false here and we should be good right?> > Dave, after testing confirms the fix, pls queue up for stable. > > > > > > drivers/net/virtio_net.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > index 4d7d5434cc5d..7b8805b47f0d 100644 > > --- a/drivers/net/virtio_net.c > > +++ b/drivers/net/virtio_net.c > > @@ -2971,6 +2971,15 @@ static int virtnet_validate(struct virtio_device *vdev) > > if (!virtnet_validate_features(vdev)) > > return -EINVAL; > > > > + /* VIRTIO_NET_F_CTRL_GUEST_OFFLOADS does not work without > > + * VIRTIO_NET_F_CTRL_VQ. However the virtio spec does not > > + * specify that VIRTIO_NET_F_CTRL_GUEST_OFFLOADS depends > > + * on VIRTIO_NET_F_CTRL_VQ so devices can set the later but > > + * not the former. > > + */ > > + if (!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) > > + __virtio_clear_bit(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS); > > + > > if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) { > > int mtu = virtio_cread16(vdev, > > offsetof(struct virtio_net_config, > > -- > > MST > >