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 Perez Martin <eperezma@redhat.com>
> Sent: Wednesday, August 26, 2020 8:51 PM
> To: Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Adrian Moreno Zapata <amorenoz@redhat.com>; Maxime
> Coquelin <maxime.coquelin@redhat.com>; stable@dpdk.org; Wang, Zhihong
> <zhihong.wang@intel.com>
> Subject: Re: [PATCH 1/1] vhost: fix iotlb mempool single-consumer flag
> 
> Hi Chenbo.
> 
> On Wed, Aug 26, 2020 at 8:29 AM Xia, Chenbo <chenbo.xia@intel.com> wrote:
> >
> > 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?
> 
> Sure, I just wanted to give enough information to reproduce it, but
> that can be in the bugzilla case too if you prefer. Do you need me to
> send a v2?
> 

Yes, the information is very detailed for review! Since there's already one
warning for commits message in patchwork, I'd like a brief description
with bugzilla link and the details could be in that link. Is this ok for you?

Thanks!
Chenbo  

> Thanks!
> 
> >
> > 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
> >