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().
  ...

1 files changed, 502 insertions, 0 deletions

diff --git a/tools/perf/pmu-events/metric.py b/tools/perf/pmu-events/metric.py
new file mode 100644
index 000000000..4797ed4fd
--- /dev/null
+++ b/tools/perf/pmu-events/metric.py
@@ -0,0 +1,502 @@
+# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+"""Parse or generate representations of perf metrics."""
+import ast
+import decimal
+import json
+import re
+from typing import Dict, List, Optional, Set, Union
+
+
+class Expression:
+  """Abstract base class of elements in a metric expression."""
+
+  def ToPerfJson(self) -> str:
+    """Returns a perf json file encoded representation."""
+    raise NotImplementedError()
+
+  def ToPython(self) -> str:
+    """Returns a python expr parseable representation."""
+    raise NotImplementedError()
+
+  def Simplify(self):
+    """Returns a simplified version of self."""
+    raise NotImplementedError()
+
+  def Equals(self, other) -> bool:
+    """Returns true when two expressions are the same."""
+    raise NotImplementedError()
+
+  def __str__(self) -> str:
+    return self.ToPerfJson()
+
+  def __or__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('|', self, other)
+
+  def __ror__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('|', other, self)
+
+  def __xor__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('^', self, other)
+
+  def __and__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('&', self, other)
+
+  def __lt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('<', self, other)
+
+  def __gt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('>', self, other)
+
+  def __add__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('+', self, other)
+
+  def __radd__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('+', other, self)
+
+  def __sub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('-', self, other)
+
+  def __rsub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('-', other, self)
+
+  def __mul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('*', self, other)
+
+  def __rmul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('*', other, self)
+
+  def __truediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('/', self, other)
+
+  def __rtruediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('/', other, self)
+
+  def __mod__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('%', self, other)
+
+
+def _Constify(val: Union[bool, int, float, Expression]) -> Expression:
+  """Used to ensure that the nodes in the expression tree are all Expression."""
+  if isinstance(val, bool):
+    return Constant(1 if val else 0)
+  if isinstance(val, (int, float)):
+    return Constant(val)
+  return val
+
+
+# Simple lookup for operator precedence, used to avoid unnecessary
+# brackets. Precedence matches that of python and the simple expression parser.
+_PRECEDENCE = {
+    '|': 0,
+    '^': 1,
+    '&': 2,
+    '<': 3,
+    '>': 3,
+    '+': 4,
+    '-': 4,
+    '*': 5,
+    '/': 5,
+    '%': 5,
+}
+
+
+class Operator(Expression):
+  """Represents a binary operator in the parse tree."""
+
+  def __init__(self, operator: str, lhs: Union[int, float, Expression],
+               rhs: Union[int, float, Expression]):
+    self.operator = operator
+    self.lhs = _Constify(lhs)
+    self.rhs = _Constify(rhs)
+
+  def Bracket(self,
+              other: Expression,
+              other_str: str,
+              rhs: bool = False) -> str:
+    """If necessary brackets the given other value.
+
+    If ``other`` is an operator then a bracket is necessary when
+    this/self operator has higher precedence. Consider: '(a + b) * c',
+    ``other_str`` will be 'a + b'. A bracket is necessary as without
+    the bracket 'a + b * c' will evaluate 'b * c' first. However, '(a
+    * b) + c' doesn't need a bracket as 'a * b' will always be
+    evaluated first. For 'a / (b * c)' (ie the same precedence level
+    operations) then we add the bracket to best match the original
+    input, but not for '(a / b) * c' where the bracket is unnecessary.
+
+    Args:
+      other (Expression): is a lhs or rhs operator
+      other_str (str): ``other`` in the appropriate string form
+      rhs (bool):  is ``other`` on the RHS
+
+    Returns:
+      str: possibly bracketed other_str
+    """
+    if isinstance(other, Operator):
+      if _PRECEDENCE.get(self.operator, -1) > _PRECEDENCE.get(
+          other.operator, -1):
+        return f'({other_str})'
+      if rhs and _PRECEDENCE.get(self.operator, -1) == _PRECEDENCE.get(
+          other.operator, -1):
+        return f'({other_str})'
+    return other_str
+
+  def ToPerfJson(self):
+    return (f'{self.Bracket(self.lhs, self.lhs.ToPerfJson())} {self.operator} '
+            f'{self.Bracket(self.rhs, self.rhs.ToPerfJson(), True)}')
+
+  def ToPython(self):
+    return (f'{self.Bracket(self.lhs, self.lhs.ToPython())} {self.operator} '
+            f'{self.Bracket(self.rhs, self.rhs.ToPython(), True)}')
+
+  def Simplify(self) -> Expression:
+    lhs = self.lhs.Simplify()
+    rhs = self.rhs.Simplify()
+    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
+      return Constant(ast.literal_eval(lhs + self.operator + rhs))
+
+    if isinstance(self.lhs, Constant):
+      if self.operator in ('+', '|') and lhs.value == '0':
+        return rhs
+
+      # Simplify multiplication by 0 except for the slot event which
+      # is deliberately introduced using this pattern.
+      if self.operator == '*' and lhs.value == '0' and (
+          not isinstance(rhs, Event) or 'slots' not in rhs.name.lower()):
+        return Constant(0)
+
+      if self.operator == '*' and lhs.value == '1':
+        return rhs
+
+    if isinstance(rhs, Constant):
+      if self.operator in ('+', '|') and rhs.value == '0':
+        return lhs
+
+      if self.operator == '*' and rhs.value == '0':
+        return Constant(0)
+
+      if self.operator == '*' and self.rhs.value == '1':
+        return lhs
+
+    return Operator(self.operator, lhs, rhs)
+
+  def Equals(self, other: Expression) -> bool:
+    if isinstance(other, Operator):
+      return self.operator == other.operator and self.lhs.Equals(
+          other.lhs) and self.rhs.Equals(other.rhs)
+    return False
+
+
+class Select(Expression):
+  """Represents a select ternary in the parse tree."""
+
+  def __init__(self, true_val: Union[int, float, Expression],
+               cond: Union[int, float, Expression],
+               false_val: Union[int, float, Expression]):
+    self.true_val = _Constify(true_val)
+    self.cond = _Constify(cond)
+    self.false_val = _Constify(false_val)
+
+  def ToPerfJson(self):
+    true_str = self.true_val.ToPerfJson()
+    cond_str = self.cond.ToPerfJson()
+    false_str = self.false_val.ToPerfJson()
+    return f'({true_str} if {cond_str} else {false_str})'
+
+  def ToPython(self):
+    return (f'Select({self.true_val.ToPython()}, {self.cond.ToPython()}, '
+            f'{self.false_val.ToPython()})')
+
+  def Simplify(self) -> Expression:
+    cond = self.cond.Simplify()
+    true_val = self.true_val.Simplify()
+    false_val = self.false_val.Simplify()
+    if isinstance(cond, Constant):
+      return false_val if cond.value == '0' else true_val
+
+    if true_val.Equals(false_val):
+      return true_val
+
+    return Select(true_val, cond, false_val)
+
+  def Equals(self, other: Expression) -> bool:
+    if isinstance(other, Select):
+      return self.cond.Equals(other.cond) and self.false_val.Equals(
+          other.false_val) and self.true_val.Equals(other.true_val)
+    return False
+
+
+class Function(Expression):
+  """A function in an expression like min, max, d_ratio."""
+
+  def __init__(self,
+               fn: str,
+               lhs: Union[int, float, Expression],
+               rhs: Optional[Union[int, float, Expression]] = None):
+    self.fn = fn
+    self.lhs = _Constify(lhs)
+    self.rhs = _Constify(rhs)
+
+  def ToPerfJson(self):
+    if self.rhs:
+      return f'{self.fn}({self.lhs.ToPerfJson()}, {self.rhs.ToPerfJson()})'
+    return f'{self.fn}({self.lhs.ToPerfJson()})'
+
+  def ToPython(self):
+    if self.rhs:
+      return f'{self.fn}({self.lhs.ToPython()}, {self.rhs.ToPython()})'
+    return f'{self.fn}({self.lhs.ToPython()})'
+
+  def Simplify(self) -> Expression:
+    lhs = self.lhs.Simplify()
+    rhs = self.rhs.Simplify() if self.rhs else None
+    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
+      if self.fn == 'd_ratio':
+        if rhs.value == '0':
+          return Constant(0)
+        Constant(ast.literal_eval(f'{lhs} / {rhs}'))
+      return Constant(ast.literal_eval(f'{self.fn}({lhs}, {rhs})'))
+
+    return Function(self.fn, lhs, rhs)
+
+  def Equals(self, other: Expression) -> bool:
+    if isinstance(other, Function):
+      return self.fn == other.fn and self.lhs.Equals(
+          other.lhs) and self.rhs.Equals(other.rhs)
+    return False
+
+
+def _FixEscapes(s: str) -> str:
+  s = re.sub(r'([^\\]),', r'\1\\,', s)
+  return re.sub(r'([^\\])=', r'\1\\=', s)
+
+
+class Event(Expression):
+  """An event in an expression."""
+
+  def __init__(self, name: str, legacy_name: str = ''):
+    self.name = _FixEscapes(name)
+    self.legacy_name = _FixEscapes(legacy_name)
+
+  def ToPerfJson(self):
+    result = re.sub('/', '@', self.name)
+    return result
+
+  def ToPython(self):
+    return f'Event(r"{self.name}")'
+
+  def Simplify(self) -> Expression:
+    return self
+
+  def Equals(self, other: Expression) -> bool:
+    return isinstance(other, Event) and self.name == other.name
+
+
+class Constant(Expression):
+  """A constant within the expression tree."""
+
+  def __init__(self, value: Union[float, str]):
+    ctx = decimal.Context()
+    ctx.prec = 20
+    dec = ctx.create_decimal(repr(value) if isinstance(value, float) else value)
+    self.value = dec.normalize().to_eng_string()
+    self.value = self.value.replace('+', '')
+    self.value = self.value.replace('E', 'e')
+
+  def ToPerfJson(self):
+    return self.value
+
+  def ToPython(self):
+    return f'Constant({self.value})'
+
+  def Simplify(self) -> Expression:
+    return self
+
+  def Equals(self, other: Expression) -> bool:
+    return isinstance(other, Constant) and self.value == other.value
+
+
+class Literal(Expression):
+  """A runtime literal within the expression tree."""
+
+  def __init__(self, value: str):
+    self.value = value
+
+  def ToPerfJson(self):
+    return self.value
+
+  def ToPython(self):
+    return f'Literal({self.value})'
+
+  def Simplify(self) -> Expression:
+    return self
+
+  def Equals(self, other: Expression) -> bool:
+    return isinstance(other, Literal) and self.value == other.value
+
+
+def min(lhs: Union[int, float, Expression], rhs: Union[int, float,
+                                                       Expression]) -> Function:
+  # pylint: disable=redefined-builtin
+  # pylint: disable=invalid-name
+  return Function('min', lhs, rhs)
+
+
+def max(lhs: Union[int, float, Expression], rhs: Union[int, float,
+                                                       Expression]) -> Function:
+  # pylint: disable=redefined-builtin
+  # pylint: disable=invalid-name
+  return Function('max', lhs, rhs)
+
+
+def d_ratio(lhs: Union[int, float, Expression],
+            rhs: Union[int, float, Expression]) -> Function:
+  # pylint: disable=redefined-builtin
+  # pylint: disable=invalid-name
+  return Function('d_ratio', lhs, rhs)
+
+
+def source_count(event: Event) -> Function:
+  # pylint: disable=redefined-builtin
+  # pylint: disable=invalid-name
+  return Function('source_count', event)
+
+
+class Metric:
+  """An individual metric that will specifiable on the perf command line."""
+  groups: Set[str]
+  expr: Expression
+  scale_unit: str
+  constraint: bool
+
+  def __init__(self,
+               name: str,
+               description: str,
+               expr: Expression,
+               scale_unit: str,
+               constraint: bool = False):
+    self.name = name
+    self.description = description
+    self.expr = expr.Simplify()
+    # Workraound valid_only_metric hiding certain metrics based on unit.
+    scale_unit = scale_unit.replace('/sec', ' per sec')
+    if scale_unit[0].isdigit():
+      self.scale_unit = scale_unit
+    else:
+      self.scale_unit = f'1{scale_unit}'
+    self.constraint = constraint
+    self.groups = set()
+
+  def __lt__(self, other):
+    """Sort order."""
+    return self.name < other.name
+
+  def AddToMetricGroup(self, group):
+    """Callback used when being added to a MetricGroup."""
+    self.groups.add(group.name)
+
+  def Flatten(self) -> Set['Metric']:
+    """Return a leaf metric."""
+    return set([self])
+
+  def ToPerfJson(self) -> Dict[str, str]:
+    """Return as dictionary for Json generation."""
+    result = {
+        'MetricName': self.name,
+        'MetricGroup': ';'.join(sorted(self.groups)),
+        'BriefDescription': self.description,
+        'MetricExpr': self.expr.ToPerfJson(),
+        'ScaleUnit': self.scale_unit
+    }
+    if self.constraint:
+      result['MetricConstraint'] = 'NO_NMI_WATCHDOG'
+
+    return result
+
+
+class _MetricJsonEncoder(json.JSONEncoder):
+  """Special handling for Metric objects."""
+
+  def default(self, o):
+    if isinstance(o, Metric):
+      return o.ToPerfJson()
+    return json.JSONEncoder.default(self, o)
+
+
+class MetricGroup:
+  """A group of metrics.
+
+  Metric groups may be specificd on the perf command line, but within
+  the json they aren't encoded. Metrics may be in multiple groups
+  which can facilitate arrangements similar to trees.
+  """
+
+  def __init__(self, name: str, metric_list: List[Union[Metric,
+                                                        'MetricGroup']]):
+    self.name = name
+    self.metric_list = metric_list
+    for metric in metric_list:
+      metric.AddToMetricGroup(self)
+
+  def AddToMetricGroup(self, group):
+    """Callback used when a MetricGroup is added into another."""
+    for metric in self.metric_list:
+      metric.AddToMetricGroup(group)
+
+  def Flatten(self) -> Set[Metric]:
+    """Returns a set of all leaf metrics."""
+    result = set()
+    for x in self.metric_list:
+      result = result.union(x.Flatten())
+
+    return result
+
+  def ToPerfJson(self) -> str:
+    return json.dumps(sorted(self.Flatten()), indent=2, cls=_MetricJsonEncoder)
+
+  def __str__(self) -> str:
+    return self.ToPerfJson()
+
+
+class _RewriteIfExpToSelect(ast.NodeTransformer):
+
+  def visit_IfExp(self, node):
+    # pylint: disable=invalid-name
+    self.generic_visit(node)
+    call = ast.Call(
+        func=ast.Name(id='Select', ctx=ast.Load()),
+        args=[node.body, node.test, node.orelse],
+        keywords=[])
+    ast.copy_location(call, node.test)
+    return call
+
+
+def ParsePerfJson(orig: str) -> Expression:
+  """A simple json metric expression decoder.
+
+  Converts a json encoded metric expression by way of python's ast and
+  eval routine. First tokens are mapped to Event calls, then
+  accidentally converted keywords or literals are mapped to their
+  appropriate calls. Python's ast is used to match if-else that can't
+  be handled via operator overloading. Finally the ast is evaluated.
+
+  Args:
+    orig (str): String to parse.
+
+  Returns:
+    Expression: The parsed string.
+  """
+  # pylint: disable=eval-used
+  py = orig.strip()
+  py = re.sub(r'([a-zA-Z][^-+/\* \\\(\),]*(?:\\.[^-+/\* \\\(\),]*)*)',
+              r'Event(r"\1")', py)
+  py = re.sub(r'#Event\(r"([^"]*)"\)', r'Literal("#\1")', py)
+  py = re.sub(r'([0-9]+)Event\(r"(e[0-9]+)"\)', r'\1\2', py)
+  keywords = ['if', 'else', 'min', 'max', 'd_ratio', 'source_count']
+  for kw in keywords:
+    py = re.sub(rf'Event\(r"{kw}"\)', kw, py)
+
+  parsed = ast.parse(py, mode='eval')
+  _RewriteIfExpToSelect().visit(parsed)
+  parsed = ast.fix_missing_locations(parsed)
+  return _Constify(eval(compile(parsed, orig, 'eval')))