From a721c3e54b80e45cd9202e7fca29ef018bed9069 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Tue, 11 Apr 2023 21:01:55 +0300 Subject: net/sched: taprio: allow per-TC user input of FP adminStatus This is a duplication of the FP adminStatus logic introduced for tc-mqprio. Offloading is done through the tc_mqprio_qopt_offload structure embedded within tc_taprio_qopt_offload. So practically, if a device driver is written to treat the mqprio portion of taprio just like standalone mqprio, it gets unified handling of frame preemption. I would have reused more code with taprio, but this is mostly netlink attribute parsing, which is hard to transform into generic code without having something that stinks as a result. We have the same variables with the same semantics, just different nlattr type values (TCA_MQPRIO_TC_ENTRY=5 vs TCA_TAPRIO_ATTR_TC_ENTRY=12; TCA_MQPRIO_TC_ENTRY_FP=2 vs TCA_TAPRIO_TC_ENTRY_FP=3, etc) and consequently, different policies for the nest. Every time nla_parse_nested() is called, an on-stack table "tb" of nlattr pointers is allocated statically, up to the maximum understood nlattr type. That array size is hardcoded as a constant, but when transforming this into a common parsing function, it would become either a VLA (which the Linux kernel rightfully doesn't like) or a call to the allocator. Having FP adminStatus in tc-taprio can be seen as addressing the 802.1Q Annex S.3 "Scheduling and preemption used in combination, no HOLD/RELEASE" and S.4 "Scheduling and preemption used in combination with HOLD/RELEASE" use cases. HOLD and RELEASE events are emitted towards the underlying MAC Merge layer when the schedule hits a Set-And-Hold-MAC or a Set-And-Release-MAC gate operation. So within the tc-taprio UAPI space, one can distinguish between the 2 use cases by choosing whether to use the TC_TAPRIO_CMD_SET_AND_HOLD and TC_TAPRIO_CMD_SET_AND_RELEASE gate operations within the schedule, or just TC_TAPRIO_CMD_SET_GATES. A small part of the change is dedicated to refactoring the max_sdu nlattr parsing to put all logic under the "if" that tests for presence of that nlattr. Signed-off-by: Vladimir Oltean Reviewed-by: Ferenc Fejes Reviewed-by: Simon Horman Signed-off-by: Jakub Kicinski --- include/uapi/linux/pkt_sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index b8d29be91b62..51a7addc56c6 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -1252,6 +1252,7 @@ enum { TCA_TAPRIO_TC_ENTRY_UNSPEC, TCA_TAPRIO_TC_ENTRY_INDEX, /* u32 */ TCA_TAPRIO_TC_ENTRY_MAX_SDU, /* u32 */ + TCA_TAPRIO_TC_ENTRY_FP, /* u32 */ /* add new constants above here */ __TCA_TAPRIO_TC_ENTRY_CNT, -- cgit v1.2.3