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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/trace/rv/deterministic_automata.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/trace/rv/deterministic_automata.rst')
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1 files changed, 184 insertions, 0 deletions
diff --git a/Documentation/trace/rv/deterministic_automata.rst b/Documentation/trace/rv/deterministic_automata.rst new file mode 100644 index 000000000..d0638f95a --- /dev/null +++ b/Documentation/trace/rv/deterministic_automata.rst @@ -0,0 +1,184 @@ +Deterministic Automata +====================== + +Formally, a deterministic automaton, denoted by G, is defined as a quintuple: + + *G* = { *X*, *E*, *f*, x\ :subscript:`0`, X\ :subscript:`m` } + +where: + +- *X* is the set of states; +- *E* is the finite set of events; +- x\ :subscript:`0` is the initial state; +- X\ :subscript:`m` (subset of *X*) is the set of marked (or final) states. +- *f* : *X* x *E* -> *X* $ is the transition function. It defines the state + transition in the occurrence of an event from *E* in the state *X*. In the + special case of deterministic automata, the occurrence of the event in *E* + in a state in *X* has a deterministic next state from *X*. + +For example, a given automaton named 'wip' (wakeup in preemptive) can +be defined as: + +- *X* = { ``preemptive``, ``non_preemptive``} +- *E* = { ``preempt_enable``, ``preempt_disable``, ``sched_waking``} +- x\ :subscript:`0` = ``preemptive`` +- X\ :subscript:`m` = {``preemptive``} +- *f* = + - *f*\ (``preemptive``, ``preempt_disable``) = ``non_preemptive`` + - *f*\ (``non_preemptive``, ``sched_waking``) = ``non_preemptive`` + - *f*\ (``non_preemptive``, ``preempt_enable``) = ``preemptive`` + +One of the benefits of this formal definition is that it can be presented +in multiple formats. For example, using a *graphical representation*, using +vertices (nodes) and edges, which is very intuitive for *operating system* +practitioners, without any loss. + +The previous 'wip' automaton can also be represented as:: + + preempt_enable + +---------------------------------+ + v | + #============# preempt_disable +------------------+ + --> H preemptive H -----------------> | non_preemptive | + #============# +------------------+ + ^ | + | sched_waking | + +--------------+ + +Deterministic Automaton in C +---------------------------- + +In the paper "Efficient formal verification for the Linux kernel", +the authors present a simple way to represent an automaton in C that can +be used as regular code in the Linux kernel. + +For example, the 'wip' automata can be presented as (augmented with comments):: + + /* enum representation of X (set of states) to be used as index */ + enum states { + preemptive = 0, + non_preemptive, + state_max + }; + + #define INVALID_STATE state_max + + /* enum representation of E (set of events) to be used as index */ + enum events { + preempt_disable = 0, + preempt_enable, + sched_waking, + event_max + }; + + struct automaton { + char *state_names[state_max]; // X: the set of states + char *event_names[event_max]; // E: the finite set of events + unsigned char function[state_max][event_max]; // f: transition function + unsigned char initial_state; // x_0: the initial state + bool final_states[state_max]; // X_m: the set of marked states + }; + + struct automaton aut = { + .state_names = { + "preemptive", + "non_preemptive" + }, + .event_names = { + "preempt_disable", + "preempt_enable", + "sched_waking" + }, + .function = { + { non_preemptive, INVALID_STATE, INVALID_STATE }, + { INVALID_STATE, preemptive, non_preemptive }, + }, + .initial_state = preemptive, + .final_states = { 1, 0 }, + }; + +The *transition function* is represented as a matrix of states (lines) and +events (columns), and so the function *f* : *X* x *E* -> *X* can be solved +in O(1). For example:: + + next_state = automaton_wip.function[curr_state][event]; + +Graphviz .dot format +-------------------- + +The Graphviz open-source tool can produce the graphical representation +of an automaton using the (textual) DOT language as the source code. +The DOT format is widely used and can be converted to many other formats. + +For example, this is the 'wip' model in DOT:: + + digraph state_automaton { + {node [shape = circle] "non_preemptive"}; + {node [shape = plaintext, style=invis, label=""] "__init_preemptive"}; + {node [shape = doublecircle] "preemptive"}; + {node [shape = circle] "preemptive"}; + "__init_preemptive" -> "preemptive"; + "non_preemptive" [label = "non_preemptive"]; + "non_preemptive" -> "non_preemptive" [ label = "sched_waking" ]; + "non_preemptive" -> "preemptive" [ label = "preempt_enable" ]; + "preemptive" [label = "preemptive"]; + "preemptive" -> "non_preemptive" [ label = "preempt_disable" ]; + { rank = min ; + "__init_preemptive"; + "preemptive"; + } + } + +This DOT format can be transformed into a bitmap or vectorial image +using the dot utility, or into an ASCII art using graph-easy. For +instance:: + + $ dot -Tsvg -o wip.svg wip.dot + $ graph-easy wip.dot > wip.txt + +dot2c +----- + +dot2c is a utility that can parse a .dot file containing an automaton as +in the example above and automatically convert it to the C representation +presented in [3]. + +For example, having the previous 'wip' model into a file named 'wip.dot', +the following command will transform the .dot file into the C +representation (previously shown) in the 'wip.h' file:: + + $ dot2c wip.dot > wip.h + +The 'wip.h' content is the code sample in section 'Deterministic Automaton +in C'. + +Remarks +------- + +The automata formalism allows modeling discrete event systems (DES) in +multiple formats, suitable for different applications/users. + +For example, the formal description using set theory is better suitable +for automata operations, while the graphical format for human interpretation; +and computer languages for machine execution. + +References +---------- + +Many textbooks cover automata formalism. For a brief introduction see:: + + O'Regan, Gerard. Concise guide to software engineering. Springer, + Cham, 2017. + +For a detailed description, including operations, and application on Discrete +Event Systems (DES), see:: + + Cassandras, Christos G., and Stephane Lafortune, eds. Introduction to discrete + event systems. Boston, MA: Springer US, 2008. + +For the C representation in kernel, see:: + + De Oliveira, Daniel Bristot; Cucinotta, Tommaso; De Oliveira, Romulo + Silva. Efficient formal verification for the Linux kernel. In: + International Conference on Software Engineering and Formal Methods. + Springer, Cham, 2019. p. 315-332. |