On Fri, Dec 20, 2019 at 1:22 PM Alistair Delva <adelva@xxxxxxxxxx> wrote: > > On devices without control virtqueue support, such as the virtio_net > implementation in crosvm[1], attempting to configure LRO will panic the > kernel: If you'd like to try using the control virtqueue, I have a WIP patch at crrev.com/c/1968200 The downside there is that when enabling IP forwarding the guest successfully disables LRO, which AFAIK (please correct me if I'm wrong!) is generally safe when using virtio-net. My iperf tests showed a ~90% bandwidth reduction, so we'd need to force LRO back on after enabling IP forwarding if the control queue offload patch lands. > > 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 > > This happens because virtio_set_features() does not check the presence > of the control virtqueue feature, which is sanity checked by a BUG_ON > in virtnet_send_command(). > > Fix this by skipping any feature processing if the control virtqueue is > missing. This should be OK for any future feature that is added, as > presumably all of them would require control virtqueue support to notify > the endpoint that offload etc. should begin. This sounds okay to me. This does end up hitting a netdev_WARN later on though: [ 1.885957] ------------[ cut here ]------------ [ 1.888398] netdevice: eth0: failed to disable LRO! [ 1.890369] WARNING: CPU: 0 PID: 163 at /mnt/host/source/src/third_party/kernel/v5.4/net/core/dev.c:1483 dev_disable_lro+0x91/0x95 [ 1.894761] CPU: 0 PID: 163 Comm: lxd Not tainted 5.4.5 #2 [ 1.896698] Hardware name: ChromiumOS crosvm, BIOS 0 [ 1.898387] RIP: 0010:dev_disable_lro+0x91/0x95 [ 1.899877] Code: a6 4d 0f 44 f7 eb 07 49 c7 c6 af 78 60 a6 4c 89 ff e8 6a 00 00 00 48 c7 c7 dd 73 60 a6 4c 89 f6 48 89 c2 31 c0 e8 36 e2 a5 ff <0f> 0b eb 8a 53 48 83 ec 18 48 89 fb 65 48 8b 04 25 28 00 00 00 48 [ 1.905701] RSP: 0018:ffffae0fc0427d78 EFLAGS: 00010246 [ 1.907282] RAX: fe766977dd14fb00 RBX: 0000000000000001 RCX: ffffffffa683aa50 [ 1.909391] RDX: fffffffffffffe6d RSI: 0000000000000082 RDI: ffffffffa683aa20 [ 1.911503] RBP: ffff990bd3f8e050 R08: ffff0a1000000600 R09: 0000004000000000 [ 1.913613] R10: 0000000000000193 R11: ffffffffa5af56a5 R12: ffffffffa6882690 [ 1.915729] R13: ffff990bd3ec2248 R14: ffff990bd3f8e000 R15: ffff990bd3f8e000 [ 1.918555] FS: 00007ca813fff700(0000) GS:ffff990bd4c00000(0000) knlGS:0000000000000000 [ 1.920648] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.922039] CR2: 00005ba0e1789990 CR3: 00000001d1716003 CR4: 00000000003606b0 [ 1.923716] Call Trace: [ 1.924356] devinet_sysctl_forward+0x15a/0x1b9 [ 1.925444] proc_sys_call_handler+0xc3/0xe0 [ 1.926491] __vfs_write+0x3d/0x19b [ 1.927351] ? selinux_file_permission+0x8c/0x124 [ 1.928482] vfs_write+0xea/0x17f [ 1.929329] ksys_write+0x68/0xc9 [ 1.930178] do_syscall_64+0x4a/0x5d [ 1.931063] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 1.932272] RIP: 0033:0x5ba0e10655c0 [ 1.933159] Code: 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 49 c7 c2 00 00 00 00 49 c7 c0 00 00 00 00 49 c7 c1 00 00 00 00 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30 [ 1.937440] RSP: 002b:000000c00041e258 EFLAGS: 00000216 ORIG_RAX: 0000000000000001 [ 1.939224] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00005ba0e10655c0 [ 1.940897] RDX: 0000000000000001 RSI: 000000c00041e4d8 RDI: 0000000000000018 [ 1.942600] RBP: 000000c00041e2a8 R08: 0000000000000000 R09: 0000000000000000 [ 1.944310] R10: 0000000000000000 R11: 0000000000000216 R12: 000000000000000c [ 1.946007] R13: 0000000000000032 R14: 00005ba0e0fa01e8 R15: 0000000000000000 [ 1.947706] ---[ end trace 9ac0c921383f98c0 ]--- > > [1] https://chromium.googlesource.com/chromiumos/platform/crosvm/ > > Fixes: a02e8964eaf9 ("virtio-net: ethtool configurable LRO") > Cc: stable@xxxxxxxxxxxxxxx [4.20+] > Cc: Michael S. Tsirkin <mst@xxxxxxxxxx> > Cc: Jason Wang <jasowang@xxxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Cc: kernel-team@xxxxxxxxxxx > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Signed-off-by: Alistair Delva <adelva@xxxxxxxxxx> Tested-by: Stephen Barber <smbarber@xxxxxxxxxxxx> > --- > drivers/net/virtio_net.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 4d7d5434cc5d..709bcd34e485 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2560,6 +2560,9 @@ static int virtnet_set_features(struct net_device *dev, > u64 offloads; > int err; > > + if (!vi->has_cvq) > + return 0; > + > if ((dev->features ^ features) & NETIF_F_LRO) { > if (vi->xdp_queue_pairs) > return -EBUSY; > -- > 2.24.1.735.g03f4e72817-goog >
