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net/sched: taprio: allow user input of per-tc max SDU

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IEEE 802.1Q clause 12.29.1.1 "The queueMaxSDUTable structure and data
types" and 8.6.8.4 "Enhancements for scheduled traffic" talk about the
existence of a per traffic class limitation of maximum frame sizes, with
a fallback on the port-based MTU.

As far as I am able to understand, the 802.1Q Service Data Unit (SDU)
represents the MAC Service Data Unit (MSDU, i.e. L2 payload), excluding
any number of prepended VLAN headers which may be otherwise present in
the MSDU. Therefore, the queueMaxSDU is directly comparable to the
device MTU (1500 means L2 payload sizes are accepted, or frame sizes of
1518 octets, or 1522 plus one VLAN header). Drivers which offload this
are directly responsible of translating into other units of measurement.

To keep the fast path checks optimized, we keep 2 arrays in the qdisc,
one for max_sdu translated into frame length (so that it's comparable to
skb->len), and another for offloading and for dumping back to the user.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vladimir Oltean 2022-09-28 12:51:58 +03:00 • committed by Jakub Kicinski
parent aac4daa894
commit a54fc09e4c
3 changed files with 167 additions and 1 deletions
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11
include/uapi/linux/pkt_sched.h
View file

@ -1232,6 +1232,16 @@ enum {
#define TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST _BITUL(0)
#define TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD _BITUL(1)
enum {
TCA_TAPRIO_TC_ENTRY_UNSPEC,
TCA_TAPRIO_TC_ENTRY_INDEX, /* u32 */
TCA_TAPRIO_TC_ENTRY_MAX_SDU, /* u32 */
/* add new constants above here */
__TCA_TAPRIO_TC_ENTRY_CNT,
TCA_TAPRIO_TC_ENTRY_MAX = (__TCA_TAPRIO_TC_ENTRY_CNT - 1)
};
enum {
TCA_TAPRIO_ATTR_UNSPEC,
TCA_TAPRIO_ATTR_PRIOMAP, /* struct tc_mqprio_qopt */
@ -1245,6 +1255,7 @@ enum {
TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION, /* s64 */
TCA_TAPRIO_ATTR_FLAGS, /* u32 */
TCA_TAPRIO_ATTR_TXTIME_DELAY, /* u32 */
TCA_TAPRIO_ATTR_TC_ENTRY, /* nest */
__TCA_TAPRIO_ATTR_MAX,
};