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

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Eugenio,

> -----Original Message-----
> From: Eugenio Pérez <eperezma@redhat.com>
> Sent: Monday, August 10, 2020 10:11 PM
> To: dev@dpdk.org
> Cc: Adrian Moreno Zapata <amorenoz@redhat.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; stable@dpdk.org; Wang, Zhihong
> <zhihong.wang@intel.com>; Xia, Chenbo <chenbo.xia@intel.com>
> Subject: [PATCH 1/1] vhost: fix iotlb mempool single-consumer flag
> 
> 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>
> 

The fix looks fine to me. But the commit message is a little bit complicated
to me (also, some lines too long). Since this bug is clear and could be
described by something like 'control thread which handles iotlb msg and forwarding
thread which uses iotlb to translate address may modify same entry of mempool
and may cause a loop in iotlb_pending_entries list'. Do you think it makes
sense?

Thanks for the fix!
Chenbo

> --
> 
> 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.
> 
> Fixes: d012d1f293f4 ("vhost: add IOTLB helper functions")
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  lib/librte_vhost/iotlb.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/lib/librte_vhost/iotlb.c b/lib/librte_vhost/iotlb.c
> index 5b3a0c090..e0b67721b 100644
> --- a/lib/librte_vhost/iotlb.c
> +++ b/lib/librte_vhost/iotlb.c
> @@ -321,8 +321,7 @@ vhost_user_iotlb_init(struct virtio_net *dev, int
> vq_index)
>  			IOTLB_CACHE_SIZE, sizeof(struct vhost_iotlb_entry), 0,
>  			0, 0, NULL, NULL, NULL, socket,
>  			MEMPOOL_F_NO_CACHE_ALIGN |
> -			MEMPOOL_F_SP_PUT |
> -			MEMPOOL_F_SC_GET);
> +			MEMPOOL_F_SP_PUT);
>  	if (!vq->iotlb_pool) {
>  		VHOST_LOG_CONFIG(ERR,
>  				"Failed to create IOTLB cache pool (%s)\n",
> --
> 2.18.1