Re: [dpdk-dev] [PATCH 0/1] vhost: fix iotlb mempool single-consumer flag

[Eugenio Perez Martin <eperezma@redhat.com>]

On Mon, Aug 10, 2020 at 4:11 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> Bugzilla bug: 523
>
> Using testpmd as a vhost-user with iommu:
>
> /home/dpdk/build/app/dpdk-testpmd -l 1,3 \
>         --vdev net_vhost0,iface=/tmp/vhost-user1,queues=1,iommu-support=1 \
>         -- --auto-start --stats-period 5 --forward-mode=txonly
>
> And qemu with packed virtqueue:
>
>     <interface type='vhostuser'>
>       <mac address='88:67:11:5f:dd:02'/>
>       <source type='unix' path='/tmp/vhost-user1' mode='client'/>
>       <model type='virtio'/>
>       <driver name='vhost' rx_queue_size='1024' iommu='on' ats='on'/>
>       <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
>     </interface>
> ...
>
>   <qemu:commandline>
>     <qemu:arg value='-set'/>
>     <qemu:arg value='device.net1.packed=on'/>
>   </qemu:commandline>
>
> --
>
> Is it possible to consume the iotlb's entries of the mempoo from different
> threads. Thread sanitizer example output (after change rwlocks to POSIX ones):
>
> WARNING: ThreadSanitizer: data race (pid=76927)
>   Write of size 8 at 0x00017ffd5628 by thread T5:
>     #0 vhost_user_iotlb_cache_insert ../lib/librte_vhost/iotlb.c:181 (dpdk-testpmd+0x769343)
>     #1 vhost_user_iotlb_msg ../lib/librte_vhost/vhost_user.c:2380 (dpdk-testpmd+0x78e4bf)
>     #2 vhost_user_msg_handler ../lib/librte_vhost/vhost_user.c:2848 (dpdk-testpmd+0x78fcf8)
>     #3 vhost_user_read_cb ../lib/librte_vhost/socket.c:311 (dpdk-testpmd+0x770162)
>     #4 fdset_event_dispatch ../lib/librte_vhost/fd_man.c:286 (dpdk-testpmd+0x7591c2)
>     #5 ctrl_thread_init ../lib/librte_eal/common/eal_common_thread.c:193 (dpdk-testpmd+0xa2890b)
>     #6 <null> <null> (libtsan.so.0+0x2a68d)
>
>   Previous read of size 8 at 0x00017ffd5628 by thread T3:
>     #0 vhost_user_iotlb_cache_find ../lib/librte_vhost/iotlb.c:252 (dpdk-testpmd+0x76ee96)
>     #1 __vhost_iova_to_vva ../lib/librte_vhost/vhost.c:42 (dpdk-testpmd+0x77488c)
>     #2 vhost_iova_to_vva ../lib/librte_vhost/vhost.h:753 (dpdk-testpmd+0x7abeb3)
>     #3 map_one_desc ../lib/librte_vhost/virtio_net.c:497 (dpdk-testpmd+0x7abeb3)
>     #4 fill_vec_buf_packed ../lib/librte_vhost/virtio_net.c:751 (dpdk-testpmd+0x7abeb3)
>     #5 vhost_enqueue_single_packed ../lib/librte_vhost/virtio_net.c:1170 (dpdk-testpmd+0x7abeb3)
>     #6 virtio_dev_rx_single_packed ../lib/librte_vhost/virtio_net.c:1346 (dpdk-testpmd+0x7abeb3)
>     #7 virtio_dev_rx_packed ../lib/librte_vhost/virtio_net.c:1384 (dpdk-testpmd+0x7abeb3)
>     #8 virtio_dev_rx ../lib/librte_vhost/virtio_net.c:1435 (dpdk-testpmd+0x7b0654)
>     #9 rte_vhost_enqueue_burst ../lib/librte_vhost/virtio_net.c:1465 (dpdk-testpmd+0x7b0654)
>     #10 eth_vhost_tx ../drivers/net/vhost/rte_eth_vhost.c:470 (dpdk-testpmd+0x1ddfbd8)
>     #11 rte_eth_tx_burst ../lib/librte_ethdev/rte_ethdev.h:4800 (dpdk-testpmd+0x505fdb)
>     #12 pkt_burst_transmit ../app/test-pmd/txonly.c:365 (dpdk-testpmd+0x5106ad)
>     #13 run_pkt_fwd_on_lcore ../app/test-pmd/testpmd.c:2080 (dpdk-testpmd+0x4f8951)
>     #14 start_pkt_forward_on_core ../app/test-pmd/testpmd.c:2106 (dpdk-testpmd+0x4f89d7)
>     #15 eal_thread_loop ../lib/librte_eal/linux/eal_thread.c:127 (dpdk-testpmd+0xa5b20a)
>     #16 <null> <null> (libtsan.so.0+0x2a68d)
>
>   Location is global '<null>' at 0x000000000000 (rtemap_0+0x00003ffd5628)
>
>   Thread T5 'vhost-events' (tid=76933, running) created by main thread at:
>     #0 pthread_create <null> (libtsan.so.0+0x2cd42)
>     #1 rte_ctrl_thread_create ../lib/librte_eal/common/eal_common_thread.c:216 (dpdk-testpmd+0xa289e7)
>     #2 rte_vhost_driver_start ../lib/librte_vhost/socket.c:1190 (dpdk-testpmd+0x7728ef)
>     #3 vhost_driver_setup ../drivers/net/vhost/rte_eth_vhost.c:1028 (dpdk-testpmd+0x1de233d)
>     #4 eth_dev_configure ../drivers/net/vhost/rte_eth_vhost.c:1126 (dpdk-testpmd+0x1de29cc)
>     #5 rte_eth_dev_configure ../lib/librte_ethdev/rte_ethdev.c:1439 (dpdk-testpmd+0x991ce2)
>     #6 start_port ../app/test-pmd/testpmd.c:2450 (dpdk-testpmd+0x4f9b45)
>     #7 main ../app/test-pmd/testpmd.c:3777 (dpdk-testpmd+0x4fe1ac)
>
>   Thread T3 'lcore-slave-3' (tid=76931, running) created by main thread at:
>     #0 pthread_create <null> (libtsan.so.0+0x2cd42)
>     #1 rte_eal_init ../lib/librte_eal/linux/eal.c:1244 (dpdk-testpmd+0xa46e2b)
>     #2 main ../app/test-pmd/testpmd.c:3673 (dpdk-testpmd+0x4fdd75)
>
> --
>
> Or:
> WARNING: ThreadSanitizer: data race (pid=76927)
>   Write of size 1 at 0x00017ffd00f8 by thread T5:
>     #0 vhost_user_iotlb_cache_insert ../lib/librte_vhost/iotlb.c:182 (dpdk-testpmd+0x769370)
>     #1 vhost_user_iotlb_msg ../lib/librte_vhost/vhost_user.c:2380 (dpdk-testpmd+0x78e4bf)
>     #2 vhost_user_msg_handler ../lib/librte_vhost/vhost_user.c:2848 (dpdk-testpmd+0x78fcf8)
>     #3 vhost_user_read_cb ../lib/librte_vhost/socket.c:311 (dpdk-testpmd+0x770162)
>     #4 fdset_event_dispatch ../lib/librte_vhost/fd_man.c:286 (dpdk-testpmd+0x7591c2)
>     #5 ctrl_thread_init ../lib/librte_eal/common/eal_common_thread.c:193 (dpdk-testpmd+0xa2890b)
>     #6 <null> <null> (libtsan.so.0+0x2a68d)
>
>   Previous write of size 1 at 0x00017ffd00f8 by thread T3:
>     #0 vhost_user_iotlb_pending_insert ../lib/librte_vhost/iotlb.c:86 (dpdk-testpmd+0x75eb0c)
>     #1 __vhost_iova_to_vva ../lib/librte_vhost/vhost.c:58 (dpdk-testpmd+0x774926)
>     #2 vhost_iova_to_vva ../lib/librte_vhost/vhost.h:753 (dpdk-testpmd+0x7a79d1)
>     #3 virtio_dev_rx_batch_packed ../lib/librte_vhost/virtio_net.c:1295 (dpdk-testpmd+0x7a79d1)
>     #4 virtio_dev_rx_packed ../lib/librte_vhost/virtio_net.c:1376 (dpdk-testpmd+0x7a79d1)
>     #5 virtio_dev_rx ../lib/librte_vhost/virtio_net.c:1435 (dpdk-testpmd+0x7b0654)
>     #6 rte_vhost_enqueue_burst ../lib/librte_vhost/virtio_net.c:1465 (dpdk-testpmd+0x7b0654)
>     #7 eth_vhost_tx ../drivers/net/vhost/rte_eth_vhost.c:470 (dpdk-testpmd+0x1ddfbd8)
>     #8 rte_eth_tx_burst ../lib/librte_ethdev/rte_ethdev.h:4800 (dpdk-testpmd+0x505fdb)
>     #9 pkt_burst_transmit ../app/test-pmd/txonly.c:365 (dpdk-testpmd+0x5106ad)
>     #10 run_pkt_fwd_on_lcore ../app/test-pmd/testpmd.c:2080 (dpdk-testpmd+0x4f8951)
>     #11 start_pkt_forward_on_core ../app/test-pmd/testpmd.c:2106 (dpdk-testpmd+0x4f89d7)
>     #12 eal_thread_loop ../lib/librte_eal/linux/eal_thread.c:127 (dpdk-testpmd+0xa5b20a)
>     #13 <null> <null> (libtsan.so.0+0x2a68d)
>
> --
>
> As a consequence, the two threads can modify the same entry of the mempool.
> Usually, this cause a loop in iotlb_pending_entries list.
>
> This behavior is only observed on packed vq + virtio-net kernel driver in the
> guest, so we could make the single-consumer flag optional. However, I have not
> found why I cannot see the issue in split, so the safer option is to never set
> it.
>
> Any comments?
>
> Thanks!
>
> Eugenio Pérez (1):
>   vhost: fix iotlb mempool single-consumer flag
>
>  lib/librte_vhost/iotlb.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> --
> 2.18.1
>

Hi! Just a friendly ping on this. Should I CC somebody else?

Thanks!