Re: [dpdk-dev] [PATCH 3/3] net/bonding: start ethdev prior to setting 8023ad flow

Dne 2021-07-12 15:07, Ori Kam napsal:

Hi Jan,

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-----Original Message-----
From: Jan Viktorin <redacted>
Sent: Monday, July 12, 2021 12:46 AM

On Sun, 11 Jul 2021 08:49:18 +0000
Ori Kam [off-list ref] wrote:

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Hi Jan,

Hi Ori,

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-----Original Message-----
From: dev <redacted> On Behalf Of Jan Viktorin
Sent: Wednesday, July 7, 2021 6:54 PM

On Sun, 4 Jul 2021 15:18:01 +0000
Matan Azrad [off-list ref] wrote:

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From: Havlík Martin

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Dne 2021-06-23 09:04, Min Hu (Connor) napsal:

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在 2021/6/22 17:25, Martin Havlik 写道:

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When dedicated queues are enabled, mlx5 PMD fails to install
RTE Flows if the underlying ethdev is not started:
bond_ethdev_8023ad_flow_set(267) -

bond_ethdev_8023ad_flow_set:

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port

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not started (slave_port=0 queue_id=1)

Why mlx5 PMD doing flow create relys on port started ?
I noticed other PMDs did not has that reliance.

After looking into it, I really can't answer this mlx5 centered
question. Closest related info we found so far is the 5th point
in https://doc.dpdk.org/guides/prog_guide/rte_flow.html#caveats
but it only specifies it's the application's responsibility and
that flow rules are assumed invalid after port
stop/close/restart but doesn't say anything about <stop - flow
rule create - start> vs <stop - start - flow rule create> where
the former is the point of failure on mlx5. I'm addressing the
maintainers for mlx5, who might know a bit more on the topic.

Hello Matan,

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From rte_ethdev.h

* Please note that some configuration is not stored between calls
to
 * rte_eth_dev_stop()/rte_eth_dev_start(). The following
configuration will
 * be retained:
 *
 *     - MTU
 *     - flow control settings
 *     - receive mode configuration (promiscuous mode, all-multicast
mode,
 *       hardware checksum mode, RSS/VMDQ settings etc.)
 *     - VLAN filtering configuration
 *     - default MAC address
 *     - MAC addresses supplied to MAC address array
 *     - flow director filtering mode (but not filtering rules)
 *     - NIC queue statistics mappings

just after this section, you can find the following statement:

 * Any other configuration will not be stored and will need to be
re-entered
 * before a call to rte_eth_dev_start().

It is not very clear how is this exactly related to flows (and this
applies for all the quoted section, I think) but at least it can be used as a

counter argument.

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I agree the doc is not clear, as I see it flows are not part of
configuration, at least not when we are talking about rte_flow.

Agree.

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Mlx5 assumes flows are allowed to be configured only after
rte_eth_dev_start(). Before start \ after stop - no flow is valid
anymore.

I believe that this discussion is not about validity of flows. Let
the flows be invalid after calling to rte_eth_dev_stop(). This is
OK, flows must be recreated and the bonding driver works this way.
But why not *before start*?

Think about it this way by changing the configuration you may create
invalid flows, for example, you can only change the number of queues
after port stop, so if you create a flow with jump to queue 3 and then
you remove queue 3 then, the flow that is cached is not valid anymore.
This goes for other configuration that may affect the validity of a flow.

This is a valid argument, of course. The thing is whether it is a 
responsibility
of the PMD to take care of those corner cases or if this is up to the
application developer. If we respect the fact that calling to stop 
invalidates all
flows then when you do:

 > port stop 0
 > flow create 0 ingress pattern ... / end actions queue 6 / end  > 
port config
rxq 3  > port start 0

it's clear that something is really wrong with the caller/user. I 
would say that
this is an application bug. I would expect that you first reconfigure 
port and
after that you modify flows. It seems quite logical and intuitive, 
doesn't it?

I agree the use case I described is bad programming, but the same logic 
can be
applied on stopping the port why flows should be deleted?
And even more important on some HW and some flows can only be inserted 
after
start since there is no real traffic gate, basically the start means
adding the flows
if a flow is in the HW it is working, adding a gate will result in PPS
degradation.

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Anyway, the PMD can possibly catch this rxq inconsistency but I can 
imagine
that there are more complicated sitations than just changing count of
queues. Any idea for a more complex real case?

Some of the resource may be created only after start,
But I don't have a very good example now.

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Martin Havlik, can you please check how ixgbe and i40e behave in the 
case
above with "rxq change after flow created"?

Both PMDs do not raise any errors in the mentioned case. The packets 
that should go to the non-existent queue are dropped at some point in 
the processing (from what I could see and understand).

I'm glad for the discussion that is taking place but I feel we have 
strayed from the original reason of it. That being the inability to 
enable dedicated queues for bonding mode 8023AD on mlx5. We have 
concluded that flow creation has to be done after port/device start. So 
moving the function call to create the flow after device start should 
solve the issue 
(https://mails.dpdk.org/archives/dev/2021-June/212210.html). From my 
testing, flow create after start is not a problem on Intel PMDs.

I'm turning to you, Connor, as you have made the original question on 
this. Is the patch I presented applicable?

Martin

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Does somebody know how other drivers behaves in this situation? (We
know and can check for Intel, there it does not seem to be an
issue.)

By the way, the mlx5 behaviour opens a (probably short) time window
between starting of a port and configuation of filtering flows. You
may want to start the port with thousands of flows that apply just
when the port starts (not after, that's late). This may introduce
glitches in filtering and measuring of traffic (well, it is a question how

serious issue could it be...).

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Agree but this is always true nothing is done is zero time and even if
it was the insertion is not in zero time, (assuming that even if the
flows are stored by the PMD until start they still will not all be
inserted in the same time)

Sorry, I probably do not understand well. Yes, creation of a flow 
would never
be zero time, agree. But if I create flows before the port starts, 
than I do not
have to care too much about how long the creation takes. Because the 
card is
expected to be configured already before pushing the "start button".

Maybe, you assume that the created flows would first be cached inside 
the
PMD and when the port is finally started, it than transparently write 
the
queues to the HW. But this is not what I was talking about, that's 
maybe even
worse because you are hiding such behaviour from users...

(I do not know the exact mlx5 implementation details, so my answer can
miss something, sorry for that.)

You are correct this is HW/PMD implementation issue, in case of Nvidia 
we must
cache the flows and only insert it after start.
Since RTE flow is generic and HW is not generic sometimes the PMD needs 
to
translate this difference and in this gray area there is a game between
best API best performance understanding what the user really wants.
This is why the doc should be very clear on what is the expected.
but this is also the reason why such document is very hard to agree on.

Ori

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This matters for the bonding case as well, doesn't it?. It is not
desirable to accidently omit a packet that was received by primary
ingress logic instead of being redirected into the dedicated queue.

Are there any chances that for mlx5 it would be possible to insert
flow rules before calling rte_eth_dev_start? Anyway, the behaviour
should be specified and documented in DPDK more precisely to avoid
such uncertainty in the future.

I agree the documentation should be fixed.

+1

Jan

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Ori

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Jan

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Matan

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Signed-off-by: Martin Havlik <redacted>
Cc: Jan Viktorin <redacted>
---
  drivers/net/bonding/rte_eth_bond_pmd.c | 26
++++++++++++++++++--------
  1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c

b/drivers/net/bonding/rte_eth_bond_pmd.c
index a6755661c..fea3bc537 100644

--- a/drivers/net/bonding/rte_eth_bond_pmd.c
+++ b/drivers/net/bonding/rte_eth_bond_pmd.c

@@ -1818,25 +1818,35 @@ slave_configure(struct rte_eth_dev

*bonded_eth_dev,

rte_flow_destroy(slave_eth_dev->data->port_id,

                                     internals-

mode4.dedicated_queues.flow[slave_eth_dev->data->port_id],

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                                     &flow_error);
+    }
  +  /* Start device */
+    errval = rte_eth_dev_start(slave_eth_dev->data->port_id);
+    if (errval != 0) {
+            RTE_BOND_LOG(ERR, "rte_eth_dev_start: port=%u,
+ err
(%d)",
+                            slave_eth_dev->data->port_id,
errval);
+            return -1;
+    }
+
+    if (internals->mode == BONDING_MODE_8023AD &&
+
+ internals->mode4.dedicated_queues.enabled
== 1)
+ {
             errval = bond_ethdev_8023ad_flow_set(bonded_eth_dev,
                             slave_eth_dev->data->port_id);
             if (errval != 0) {
                     RTE_BOND_LOG(ERR,
                             "bond_ethdev_8023ad_flow_set:
port=%d, err (%d)", slave_eth_dev->data->port_id, errval);
+
+                    errval =
rte_eth_dev_stop(slave_eth_dev->data->port_id);
+                    if (errval < 0) {
+                            RTE_BOND_LOG(ERR,
+                                    "rte_eth_dev_stop:
+ port=%d,
err (%d)",
+
slave_eth_dev->data->port_id, errval);
+                    }
                     return errval;
             }
     }
  -  /* Start device */
-    errval = rte_eth_dev_start(slave_eth_dev->data->port_id);
-    if (errval != 0) {
-            RTE_BOND_LOG(ERR, "rte_eth_dev_start: port=%u, err
(%d)",
-                            slave_eth_dev->data->port_id,
errval);
-            return -1;
-    }
-
     /* If RSS is enabled for bonding, synchronize RETA */
     if (bonded_eth_dev->data->dev_conf.rxmode.mq_mode &
ETH_MQ_RX_RSS) {
             int i;