@Olivier, please, take a look at the end of the mail.
On 10/29/19 8:19 PM, Slava Ovsiienko wrote:
Hi, Andrew
Thank you for the review.
-----Original Message-----
From: Andrew Rybchenko <arybche...@solarflare.com>
Sent: Tuesday, October 29, 2019 18:22
To: Slava Ovsiienko <viachesl...@mellanox.com>; dev@dpdk.org
Cc: Thomas Monjalon <tho...@monjalon.net>; Matan Azrad
<ma...@mellanox.com>; olivier.m...@6wind.com; Ori Kam
<or...@mellanox.com>; Yongseok Koh <ys...@mellanox.com>
Subject: Re: [dpdk-dev] [PATCH v4] ethdev: extend flow metadata
On 10/27/19 9:40 PM, Viacheslav Ovsiienko wrote:
Currently, metadata can be set on egress path via mbuf tx_metadata
field with PKT_TX_METADATA flag and RTE_FLOW_ITEM_TYPE_META
matches metadata.
This patch extends the metadata feature usability.
1) RTE_FLOW_ACTION_TYPE_SET_META
When supporting multiple tables, Tx metadata can also be set by a rule
and matched by another rule. This new action allows metadata to be set
as a result of flow match.
2) Metadata on ingress
There's also need to support metadata on ingress. Metadata can be set
by SET_META action and matched by META item like Tx. The final value
set by the action will be delivered to application via metadata
dynamic field of mbuf which can be accessed by
RTE_FLOW_DYNF_METADATA().
PKT_RX_DYNF_METADATA flag will be set along with the data.
The mbuf dynamic field must be registered by calling
rte_flow_dynf_metadata_register() prior to use SET_META action.
The availability of dynamic mbuf metadata field can be checked with
rte_flow_dynf_metadata_avail() routine.
For loopback/hairpin packet, metadata set on Rx/Tx may or may not be
propagated to the other path depending on hardware capability.
Signed-off-by: Yongseok Koh <ys...@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viachesl...@mellanox.com>
Above explanations lack information about "meta" vs "mark" which may be
set on Rx as well and delivered in other mbuf field.
It should be explained by one more field is required and rules defined.
There is some story about metadata features.
Initially, there were proposed two metadata related actions:
- RTE_FLOW_ACTION_TYPE_FLAG
- RTE_FLOW_ACTION_TYPE_MARK
These actions set the special flag in the packet metadata, MARK action stores
some
specified value in the metadata storage, and, on the packet receiving PMD puts
the flag
and value to the mbuf and applications can see the packet was threated inside
flow engine
according to the appropriate RTE flow(s). MARK and FLAG are like some kind of
gateway
to transfer some per-packet information from the flow engine to the application
via receiving datapath.
From the datapath point of view, the MARK and FLAG are related to the
receiving side only.
It would useful to have the same gateway on the transmitting side and there was
the feature
of type RTE_FLOW_ITEM_TYPE_META was proposed. The application can fill the
field in mbuf
and this value will be transferred to some field in the packet metadata inside
the flow engine.
It did not matter whether these metadata fields are shared because of MARK and
META items
belonged to different domains (receiving and transmitting) and could be
vendor-specific.
So far, so good, DPDK proposes some entities to control metadata inside the
flow engine
and gateways to exchange these values on a per-packet basis via datapaths.
As we can see, the MARK and META means are not symmetric, there is absent
action which
would allow us to set META value on the transmitting path. So, the action of
type:
- RTE_FLOW_ACTION_TYPE_SET_META is proposed.
The next, applications raise the new requirements for packet metadata. The flow
engines are
getting more complex, internal switches are introduced, multiple ports might be
supported within
the same flow engine namespace. From the DPDK points of view, it means the
packets might be sent
on one eth_dev port and received on the other one, and the packet path inside
the flow engine entirely
belongs to the same hardware device. The simplest example is SR-IOV with PF,
VFs and the representors.
And there is a brilliant opportunity to provide some out-of-band channel to
transfer some extra data
from one port to another one, besides the packet data itself.
Above explanations lack information about "meta" vs "mark" which may be
set on Rx as well and delivered in other mbuf field.
It should be explained by one more field is required and rules defined.
Otherwise we can endup in half PMDs supporting mark only, half PMDs
supporting meta only and applications in an interesting situation to make a
choice which one to use.
There is no "mark" vs "meta". MARK and META means are kept for compatibility
issues
and legacy part works exactly as before. The trials (with flow_validate) is
supposed
to check whether PMD supports MARK or META feature on appropriate domain. It
depends
on PMD implementation, configuration and underlaying HW/FW/kernel capabilities
and
should be resolved in runtime.
The trials a way, but very tricky way. My imagination draws me
pictures how an application code could look like in attempt to use
either mark or meta for Rx only and these pictures are not nice.
May be it will look acceptable when mark becomes a dynamic
since usage of either one or another dynamic field is definitely
easier than usage of either fixed or dynamic field.
May be dynamic field for mark at fixed offset should be
introduced in the release or the nearest future? It will allow
to preserve ABI up to 20.11 and provide future proof API.
The trick is to register dynamic meta field at fixed offset
at start of a day to be sure that it is guaranteed to succeed.
It sounds like it is a transition mechanism from fixed to
dynamic fields.
[snip]
diff --git a/lib/librte_ethdev/rte_flow.h
b/lib/librte_ethdev/rte_flow.h index 4fee105..b821557 100644
--- a/lib/librte_ethdev/rte_flow.h
+++ b/lib/librte_ethdev/rte_flow.h
@@ -28,6 +28,8 @@
#include <rte_byteorder.h>
#include <rte_esp.h>
#include <rte_higig.h>
+#include <rte_mbuf.h>
+#include <rte_mbuf_dyn.h>
#ifdef __cplusplus
extern "C" {
@@ -418,7 +420,8 @@ enum rte_flow_item_type {
/**
* [META]
*
- * Matches a metadata value specified in mbuf metadata field.
+ * Matches a metadata value.
+ *
* See struct rte_flow_item_meta.
*/
RTE_FLOW_ITEM_TYPE_META,
@@ -1263,9 +1266,17 @@ struct rte_flow_item_icmp6_nd_opt_tla_eth {
#endif
/**
- * RTE_FLOW_ITEM_TYPE_META.
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
Is it allowed to make experimental back?
I think we should remove EXPERIMENTAL here. We do not introduce new
feature, but just extend the apply area.
Agreed.
*
- * Matches a specified metadata value.
+ * RTE_FLOW_ITEM_TYPE_META
+ *
+ * Matches a specified metadata value. On egress, metadata can be set
+ either by
+ * mbuf tx_metadata field with PKT_TX_METADATA flag or
+ * RTE_FLOW_ACTION_TYPE_SET_META. On ingress,
+ RTE_FLOW_ACTION_TYPE_SET_META sets
+ * metadata for a packet and the metadata will be reported via mbuf
+ metadata
+ * dynamic field with PKT_RX_DYNF_METADATA flag. The dynamic mbuf
+ field must be
+ * registered in advance by rte_flow_dynf_metadata_register().
*/
struct rte_flow_item_meta {
rte_be32_t data;
[snip]
@@ -2429,6 +2447,55 @@ struct rte_flow_action_set_mac {
uint8_t mac_addr[RTE_ETHER_ADDR_LEN];
};
+/**
+ * @warning
+ * @b EXPERIMENTAL: this structure may change without prior notice
+ *
+ * RTE_FLOW_ACTION_TYPE_SET_META
+ *
+ * Set metadata. Metadata set by mbuf tx_metadata field with
+ * PKT_TX_METADATA flag on egress will be overridden by this action.
+On
+ * ingress, the metadata will be carried by mbuf metadata dynamic
+field
+ * with PKT_RX_DYNF_METADATA flag if set. The dynamic mbuf field
+must be
+ * registered in advance by rte_flow_dynf_metadata_register().
+ *
+ * Altering partial bits is supported with mask. For bits which have
+never
+ * been set, unpredictable value will be seen depending on driver
+ * implementation. For loopback/hairpin packet, metadata set on Rx/Tx
+may
+ * or may not be propagated to the other path depending on HW
capability.
+ *
+ * RTE_FLOW_ITEM_TYPE_META matches metadata.
+ */
+struct rte_flow_action_set_meta {
+ rte_be32_t data;
+ rte_be32_t mask;
As I understand tx_metadata is host endian. Just double-checking.
Is a new dynamic field host endian or big endian?
I definitely would like to see motivation in comments why data/mask are big-
endian here.
metadata is opaque value, endianness does not matter, there are no some
special motivations for choosing endiannes. rte_flow_item_meta() structure
provides data with rte_be32_t type, so meta related action does the same.
Endianness of meta in mbuf and flow API should match and it must be
documented. Endianness is important if a HW supports less bits since
it makes a hit for application to use LSB first if the bit space is
sufficient.
mark is defined as host-endian (uint32_t) and I think meta should be the
same. Otherwise it complicates even more either mark or meta usage
as discussed above .
Yes, I think that rte_flow_item_meta should be fixed since both
mark and tx_metadata are host-endian.
(it says nothing about HW interface which is vendor specific and
vendor PMDs should care about it)
I could assume the origin of selecting bigendian type was the endianness
of metadata field in Tx descriptor of ConnectX NICs.
+};
+
+/* Mbuf dynamic field offset for metadata. */ extern int
+rte_flow_dynf_metadata_offs;
+
+/* Mbuf dynamic field flag mask for metadata. */ extern uint64_t
+rte_flow_dynf_metadata_mask;
These two global variables look frightening to me.
It does not look good to me.
For me too. But we need the performance, these ones are
intended for usage in datapath, any overhead is painful.
@Olivier, could you share your thoughts, please.
Andrew.
