On Tue, Dec 20, 2022 at 05:17:57PM +0800, huang...@chinatelecom.cn wrote: > From: Hyman Huang(黄勇) <huang...@chinatelecom.cn> > > v5(resend): > -rebase on master
Causes failures on some configurations: https://gitlab.com/mstredhat/qemu/-/jobs/3506121251 /usr/bin/ld: libcommon.fa.p/hw_net_vhost_net.c.o: in function `vhost_net_save_acked_features': /builds/mstredhat/qemu/build/../hw/net/vhost_net.c:150: undefined reference to `vhost_user_save_acked_features' Probably some stubs missing. > v5: > -fix the assert statement in [PATCH v4 3/3], reported by > xiangdong. > > v4: > -rebase on master > -add stub function to fix build errors > -code clean on [PATCH v2 1/2]: drop 'cleanup' parameter in > vhost_user_save_acked_features. > -code clean on [PATCH v2 2/2]: make refactor of chr_closed_bh > a standalone patch. > > Above changes are suggested by Michael and thanks very much. > > Please review, > > Yong > > v3: > -rebase on master > -code clean on [PATCH v2 1/2]: keep the commit self-consistent and > do not modify the logic of saving acked_features. Just abstract the > util function. > -modify the [PATCH v2 2/2] logic: change the behavior of saving > acked_features in chr_closed_bh: saving acked_features only if > features aren't 0. For the case of 0, we implement it in > virtio_net_set_features function, which will save the acked_features > in advance, including assign 0 to acked_features. > > v2: > Fix the typo in subject of [PATCH v2 2/2] > > v1: > This is the version 1 of the series and it is exactly the same as > RFC version, but fixing a typo in subject, which is reported by Michael. > > As for test for the behavior suggested by Michael, IMHO, it could be > post in another series, since i found that testing the negotiation > behavior using QGraph Test Framework requires more work than i thought. > > The test patch may implement the following logic... > 1. Introduce a fresh new qmp command to query netdev info, which show > the NetClient status including guest features and acked_features. > 2. Using vhost-user QGraph Test to check the behavior of the vhost user > protocol cmd VHOST_USER_SET_FEATURES. > 3. Adding acked_features into TestServer, which receive the features > set by QEMU. > 4. Compare the acked_feature in TestServer with the acked_features > in the output of qmp query command. > > Patch for RFC can be found in the following: > https://patchew.org/QEMU/20220926063641.25038-1-huang...@chinatelecom.cn/ > > This patchset aim to fix the unexpected negotiation features for > vhost-user netdev interface. > > Steps to reproduce the issue: > Prepare a vm (CentOS 8 in my work scenario) with vhost-user > backend interface and configure qemu as server mode. So dpdk > would connect qemu's unix socket periodically. > > 1. start vm in background and restart openvswitch service > concurrently and repeatedly in the process of vm start. > > 2. check if negotiated virtio features of port is "0x40000000" at > dpdk side by executing: > ovs-vsctl list interface | grep features | grep {port_socket_path} > > 3. if features equals "0x40000000", go to the vm and check if sending > arp package works, executing: > arping {IP_ADDR} > if vm interface is configured to boot with dhcp protocol, it > would get no ip. > > After doing above steps, we'll find the arping not work, the ovs on > host side has forwarded unexpected arp packages, which be added 0x0000 > in the head of ethenet frame. Though qemu report some error when > read/write cmd of vhost protocol during the process of vm start, > like the following: > > "Failed to set msg fds" > "vhost VQ 0 ring restore failed: -22: Invalid argument (22)" > > The vm does not stop or report more suggestive error message, it > seems that everthing is ok. > > The root cause is that dpdk port negotiated nothing but only one > VHOST_USER_F_PROTOCOL_FEATURES feature with vhost-user interface at > qemu side, which is an unexpected behavior. qemu only load the > VHOST_USER_F_PROTOCOL_FEATURES when VHOST_USER_SET_FEATURES and loss > the guest features configured by front-end virtio driver using the > VIRTIO_PCI_COMMON_GF addr, which is stored in acked_features field > of struct vhost_dev. > > To explain how the acked_features disappear, we may need to know the > lifecyle of acked_features in vhost_dev during feature negotiation. > > 1. qemu init acked_features field of struct vhost_dev in vhost_net_init() > by calling vhost_net_ack_features(), the init value fetched from > acked_features field of struct NetVhostUserState, which is the backup > role after vhost stopping or unix socket closed. > In the first time, the acked_features of struct NetVhostUserState is 0 > so the init value of vhost_dev's acked_features also 0. > > 2. when guest virtio driver set features, qemu accept the features and > call virtio_set_features to store the features as acked_features in > vhost_dev. > > 3. when unix socket closed or vhost_dev device doesn't work and be > stopped unexpectedly, qemu will call chr_closed_bh or vhost_user_stop, > which will copy acked_features from vhost_dev to NetVhostUserState and > cleanup the vhost_dev. Since virtio driver not allowed to set features > once status of virtio device changes to VIRTIO_CONFIG_S_FEATURE_OK, > qemu need to backup it in case of loss. > > 4. once unix socket return to normal and get connected, qemu will > call vhost_user_start to restore the vhost_dev and fetch the > acked_features stored in NetVhostUserState previously. > > The above flow works fine in the normal scenarios, but it doesn't cover > the scenario that openvswitch service restart in the same time of > virtio features negotiation. > > Let's analyze such scenario: > qemu dpdk > > vhost_net_init() > | systemctl stop openvswitch.service > virtio_set_features() | > | systemctl start openvswitch.service > virtio_set_status() > > Ovs stop service before guset setting virtio features, chr_closed_bh() > be called and fetch acked_features in vhost_dev, if may store the > incomplete features to NetVhostUserState since it doesn't include > guest features, eg "0x40000000". > > Guest set virtio features with another features, eg "0x7060a782", > this value will store in acked_features of vhost_dev, which is the > right and up-to-date features. > > After ovs service show up, qemu unix socket get connected and call > vhost_user_start(), which will restore acked_features of vhost_dev > using NetVhostUserState and "0x40000000" be loaded, which is obsolete. > > Guest set virtio device status and therefore qemu call > virtio_net_vhost_status finally, checking if vhost-net device has > started, start it if not, consequently the obsolete acked_features > "0x40000000" be negotiated after calling vhost_dev_set_features(). > > So the key point of solving this issue making the acked_features > in NetVhostUserState up-to-date, these patchset provide this > solution. > > [PATCH 1/2]: Abstract the existing code of saving acked_features > into vhost_user_save_acked_features so the next > patch seems clean. > > [PATCH 2/2]: Save the acked_features to NetVhostUserState once > Guest virtio driver configured. This step makes > acked_features in NetVhostUserState up-to-date. > > Please review, any comments and suggestions are welcome. > > Best regard. > > Yong > > Hyman Huang (3): > vhost-user: Refactor vhost acked features saving > vhost-user: Refactor the chr_closed_bh > vhost-user: Fix the virtio features negotiation flaw > > hw/net/vhost_net-stub.c | 5 +++++ > hw/net/vhost_net.c | 7 +++++++ > hw/net/virtio-net.c | 6 ++++++ > include/net/vhost-user.h | 1 + > include/net/vhost_net.h | 2 ++ > net/vhost-user.c | 27 ++++++++++++++++----------- > 6 files changed, 37 insertions(+), 11 deletions(-) > > -- > 1.8.3.1
