[Skiboot] [PATCH] dt: add /cpus/ibm, powerpc-cpu-features device tree bindings
Nicholas Piggin
npiggin at gmail.com
Sat Apr 22 11:59:55 AEST 2017
This is a new CPU feature advertising interface that is fine-grained,
extensible, aware of privilege levels, and gives control of features
to all levels of the stack (firmware, hypervisor, and OS).
The design and binding specification is described in detail in doc/.
The interface definitions are not yet finalised, so this interface is
disabled by default. This will help final testing and freezing of the
interface before it is enabled unconditionally.
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
Resending with a better changelog and compile option defaulting to
off. No other changes.
My idea was to get the Linux patch merged first, then merge the OPAL side
when the interface final. However given the documentation is mostly in
skiboot, and size of the patch and for ease of testing, it might be
easier to merge OPAL and Linux patches with temporary default to off?
Makefile | 4 +
Makefile.main | 4 +
core/Makefile.inc | 4 +
core/cpufeatures.c | 896 +++++++++++++++++++++
core/device.c | 7 +
core/init.c | 1 +
.../ibm,powerpc-cpu-features/binding.txt | 226 ++++++
.../ibm,powerpc-cpu-features/design.txt | 157 ++++
include/device.h | 1 +
include/skiboot.h | 9 +
10 files changed, 1309 insertions(+)
create mode 100644 core/cpufeatures.c
create mode 100644 doc/device-tree/ibm,powerpc-cpu-features/binding.txt
create mode 100644 doc/device-tree/ibm,powerpc-cpu-features/design.txt
diff --git a/Makefile b/Makefile
index 157eda2f..9248564d 100644
--- a/Makefile
+++ b/Makefile
@@ -47,6 +47,10 @@ ELF_ABI_v2 ?= $(LITTLE_ENDIAN)
# Discard unreferenced code and data at link-time
DEAD_CODE_ELIMINATION ?= 0
+# Provide the ibm,powerpc-cpu-features binding. This interface
+# specification is not yet finalised.
+DT_CPUFEATURES ?= 0
+
#
# Where is the source directory, must be a full path (no ~)
# Example: SRC= /home/me/skiboot
diff --git a/Makefile.main b/Makefile.main
index 54941312..abdee611 100644
--- a/Makefile.main
+++ b/Makefile.main
@@ -82,6 +82,10 @@ ifeq ($(DEAD_CODE_ELIMINATION),1)
CFLAGS += -ffunction-sections -fdata-sections
endif
+ifeq ($(DT_CPUFEATURES),1)
+CFLAGS += -DDT_CPUFEATURES=1
+endif
+
ifeq ($(SKIBOOT_GCOV),1)
CFLAGS += -fprofile-arcs -ftest-coverage -DSKIBOOT_GCOV=1
endif
diff --git a/core/Makefile.inc b/core/Makefile.inc
index b09c30c0..d4cd0f4b 100644
--- a/core/Makefile.inc
+++ b/core/Makefile.inc
@@ -10,6 +10,10 @@ CORE_OBJS += console-log.o ipmi.o time-utils.o pel.o pool.o errorlog.o
CORE_OBJS += timer.o i2c.o rtc.o flash.o sensor.o ipmi-opal.o
CORE_OBJS += flash-subpartition.o bitmap.o buddy.o pci-quirk.o
+ifeq ($(DT_CPUFEATURES),1)
+CORE_OBJS += cpufeatures.o
+endif
+
ifeq ($(SKIBOOT_GCOV),1)
CORE_OBJS += gcov-profiling.o
endif
diff --git a/core/cpufeatures.c b/core/cpufeatures.c
new file mode 100644
index 00000000..1acedc1d
--- /dev/null
+++ b/core/cpufeatures.c
@@ -0,0 +1,896 @@
+/* Copyright 2017 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * This file deals with setting up the /cpus/features device tree
+ * by discovering CPU hardware and populating feature nodes.
+ */
+
+#include <skiboot.h>
+#include <cpu.h>
+#include <ccan/str/str.h>
+#include <device.h>
+
+#ifdef DEBUG
+#define DBG(fmt, a...) prlog(PR_DEBUG, "CPUFT: " fmt, ##a)
+#else
+#define DBG(fmt, a...)
+#endif
+
+/* Device-tree visible constants follow */
+#define ISA_V2_07B 2070
+#define ISA_V3_0B 3000
+
+#define USABLE_PR (1U << 0)
+#define USABLE_OS (1U << 1)
+#define USABLE_HV (1U << 2)
+
+#define HV_SUPPORT_HFSCR (1U << 0)
+#define OS_SUPPORT_FSCR (1U << 0)
+
+/* Following are definitions for the match tables, not the DT binding itself */
+#define ISA_BASE 0
+
+#define HV_NONE 0
+#define HV_CUSTOM 1
+#define HV_HFSCR 2
+
+#define OS_NONE 0
+#define OS_CUSTOM 1
+#define OS_FSCR 2
+
+/* CPU bitmasks for match table */
+#define CPU_P8_DD1 (1U << 0)
+#define CPU_P8_DD2 (1U << 1)
+#define CPU_P9_DD1 (1U << 2)
+#define CPU_P9_DD2 (1U << 3)
+
+#define CPU_P8 (CPU_P8_DD1|CPU_P8_DD2)
+#define CPU_P9 (CPU_P9_DD1|CPU_P9_DD2)
+#define CPU_ALL (CPU_P8|CPU_P9)
+
+struct cpu_feature {
+ const char *name;
+ uint32_t cpus_supported;
+ uint32_t isa;
+ uint32_t usable_privilege;
+ uint32_t hv_support;
+ uint32_t os_support;
+ uint32_t hfscr_bit_nr;
+ uint32_t fscr_bit_nr;
+ uint32_t hwcap_bit_nr;
+ const char *dependencies_names; /* space-delimited names */
+};
+
+/*
+ * The base (or NULL) cpu feature set is the CPU features available
+ * when no child nodes of the /cpus/ibm,powerpc-cpu-features node exist. The
+ * base feature set is POWER8 (ISAv2.07B), less features that are listed
+ * explicitly.
+ *
+ * XXX: currently, the feature dependencies are not necessarily captured
+ * exactly or completely. This is somewhat acceptable because all
+ * implementations must be aware of all these features.
+ */
+static const struct cpu_feature cpu_features_table[] = {
+ /*
+ * Big endian as in ISAv2.07B, MSR_LE=0
+ */
+ { "big-endian",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * Little endian as in ISAv2.07B, MSR_LE=1.
+ *
+ * When both big and little endian are defined, there is an LPCR ILE
+ * bit and implementation specific way to switch HILE mode, MSR_SLE,
+ * etc.
+ */
+ { "little-endian",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * MSR_HV=1 mode as in ISAv2.07B (i.e., hypervisor privileged
+ * instructions and registers).
+ */
+ { "hypervisor",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV,
+ HV_CUSTOM, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B interrupt vectors, registers, and control registers
+ * (e.g., AIL, ILE, HV, etc LPCR bits).
+ *
+ * This does not necessarily specify all possible interrupt types.
+ * floating-point, for example requires some ways to handle floating
+ * point exceptions, but the low level details of interrupt handler
+ * is not a dependency there. There will always be *some* interrupt
+ * handler, (and some way to provide memory magagement, etc.).
+ */
+ { "interrupt-facilities",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ { "smt",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, 14,
+ NULL, },
+
+ /*
+ * ISAv2.07B Program Priority Registers (PPR)
+ * PPR and associated control registers (e.g. RPR, PSPB),
+ * priority "or" instructions, etc.
+ */
+ { "program-priority-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Book3S Chapter 5.7.9.1. Virtual Page Class Key Protecion
+ * AMR, IAMR, AMOR, UAMOR, etc registers and MMU key bits.
+ */
+ { "virtual-page-class-key-protection",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B SAO storage control attribute
+ */
+ { "strong-access-ordering",
+ CPU_ALL & ~CPU_P9_DD1,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B no-execute storage control attribute
+ */
+ { "no-execute",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * Cache inhibited attribute supported on large pages.
+ */
+ { "cache-inhibited-large-page",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Book3S Chapter 8. Debug Facilities
+ * CIEA, CIABR, DEAW, MEte, trace interrupt, etc.
+ * Except CFAR, branch tracing.
+ */
+ { "debug-facilities",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B CFAR
+ */
+ { "come-from-address-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ "debug-facilities", },
+
+ /*
+ * ISAv2.07B Branch tracing (optional in ISA)
+ */
+ { "branch-tracing",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ "debug-facilities", },
+
+ /*
+ * ISAv2.07B Floating-point Facility
+ */
+ { "floating-point",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(63), -1, 27,
+ NULL, },
+
+ /*
+ * ISAv2.07B Vector Facility (VMX)
+ */
+ { "vector",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(62), -1, 28,
+ "floating-point", },
+
+ /*
+ * ISAv2.07B Vector-scalar Facility (VSX)
+ */
+ { "vector-scalar",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, 7,
+ "vector", },
+
+ { "vector-crypto",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, 57,
+ "vector", },
+
+ /*
+ * ISAv2.07B Binary Coded Decimal (BCD)
+ * BCD fixed point instructions
+ */
+ { "decimal-integer",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Decimal floating-point Facility (DFP)
+ */
+ { "decimal-floating-point",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, 10,
+ "floating-point", },
+
+ /*
+ * ISAv2.07B
+ * DSCR, default data prefetch LPCR, etc
+ */
+ { "data-stream-control-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(61), PPC_BITLSHIFT(61), 61,
+ NULL, },
+
+ /*
+ * ISAv2.07B Branch History Rolling Buffer (BHRB)
+ */
+ { "branch-history-rolling-buffer",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(59), -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Transactional Memory Facility (TM or HTM)
+ */
+ { "transactional-memory",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(58), -1, 62,
+ NULL, },
+
+ /*
+ * ISAv3.0B TM additions
+ * TEXASR bit 17, self-induced vs external footprint overflow
+ */
+ { "transactional-memory-v3",
+ CPU_ALL,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "transactional-memory", },
+
+ /*
+ * ISAv2.07B Event-Based Branch Facility (EBB)
+ */
+ { "event-based-branch",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(56), PPC_BITLSHIFT(56), 60,
+ NULL, },
+
+ /*
+ * ISAv2.07B Target Address Register (TAR)
+ */
+ { "target-address-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_CUSTOM, OS_CUSTOM,
+ PPC_BITLSHIFT(55), PPC_BITLSHIFT(55), 58,
+ NULL, },
+
+ /*
+ * ISAv2.07B Control Register (CTRL)
+ */
+ { "control-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Book3S Chapter 11. Processor Control.
+ * msgsnd, msgsndp, doorbell, etc.
+ *
+ * ISAv3.0B is not compatible (different addressing, HFSCR required
+ * for msgsndp).
+ */
+ { "processor-control-facility",
+ CPU_P8_DD2, /* P8 DD1 has no dbell */
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B PURR, SPURR registers
+ */
+ { "processor-utilization-of-resources-register",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * POWER8 initiate coprocessor store word indexed (icswx) instruction
+ */
+ { "coprocessor-icswx",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B hash based MMU and all instructions, registers,
+ * data structures, exceptions, etc.
+ */
+ { "mmu-hash",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * POWER8 MCE / machine check exception.
+ */
+ { "machine-check-power8",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * POWER8 PMU / performance monitor unit.
+ */
+ { "performance-monitor-power8",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B alignment interrupts set DSISR register
+ *
+ * POWER CPUs do not used this, and it's removed from ISAv3.0B.
+ */
+ { "alignment-interrupt-dsisr",
+ 0,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B / POWER8 doze, nap, sleep, winkle instructions
+ * XXX: is Linux we using some BookIV specific implementation details
+ * in nap handling? We have no POWER8 specific key here.
+ */
+ { "idle-nap",
+ CPU_P8,
+ ISA_BASE, USABLE_HV,
+ HV_CUSTOM, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B wait instruction
+ */
+ { "wait",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ { "subcore",
+ CPU_P8,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ "smt", },
+
+ /*
+ * ISAv3.0B radix based MMU
+ */
+ { "mmu-radix",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B hash based MMU, new hash pte format, PCTR, etc
+ */
+ { "mmu-hash-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B wait instruction
+ */
+ { "wait-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B stop idle instructions and registers
+ * XXX: Same question as for idle-nap
+ */
+ { "idle-stop",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B Hypervisor Virtualization Interrupt
+ * Also associated system registers, LPCR EE, HEIC, HVICE,
+ * system reset SRR1 reason, etc.
+ */
+ { "hypervisor-virtualization-interrupt",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV,
+ HV_CUSTOM, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * POWER9 MCE / machine check exception.
+ */
+ { "machine-check-power9",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * POWER9 PMU / performance monitor unit.
+ */
+ { "performance-monitor-power9",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_CUSTOM,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B scv/rfscv system call instructions and exceptions, fscr bit
+ * etc.
+ */
+ { "system-call-vectored",
+ CPU_P9,
+ ISA_V3_0B, USABLE_OS|USABLE_PR,
+ HV_NONE, OS_CUSTOM,
+ -1, PPC_BITLSHIFT(51), -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B Book3S Chapter 10. Processor Control.
+ * global msgsnd, msgsndp, msgsync, doorbell, etc.
+ */
+ { "processor-control-facility-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_CUSTOM, OS_NONE,
+ PPC_BITLSHIFT(53), -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B addpcis instruction
+ */
+ { "pc-relative-addressing",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv2.07B Book3S Chapter 7. Timer Facilities
+ * TB, VTB, DEC, HDEC, IC, etc registers and exceptions.
+ * Not including PURR or SPURR registers.
+ */
+ { "timer-facilities",
+ CPU_ALL,
+ ISA_BASE, USABLE_HV|USABLE_OS,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B Book3S Chapter 7. Timer Facilities
+ * Large decrementer and hypervisor decrementer
+ */
+ { "timer-facilities-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "timer-facilities", },
+
+ /*
+ * ISAv3.0B deliver a random number instruction (darn)
+ */
+ { "random-number-generator",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B fixed point instructions
+ * multiply-add, modulo, count trailing zeroes, cmprb, cmpeqb,
+ * extswsli, mfvsrld, mtvsrdd, mtvsrws, addex
+ */
+ { "fixed-point-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ { "decimal-integer-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "fixed-point-v3 decimal-integer", },
+
+ /*
+ * ISAv3.0B lightweight mffs
+ */
+ { "floating-point-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "floating-point", },
+
+ { "decimal-floating-point-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "floating-point-v3 decimal-floating-point", },
+
+ { "vector-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "vector", },
+
+ { "vector-scalar-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "vector-v3 vector-scalar" },
+
+ { "vector-binary128",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, 54,
+ "vector-scalar-v3", },
+
+ { "vector-binary16",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "vector-v3", },
+
+ /*
+ * ISAv3.0B branch instruction and register additions
+ * CA32, OV32, mcrxrx, setb
+ */
+ { "branch-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B external exception for EBB
+ */
+ { "event-based-branch-v3",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ "event-based-branch", },
+
+ /*
+ * ISAv3.0B Atomic Memory Operations (AMO)
+ */
+ { "atomic-memory-operations",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B Copy-Paste Facility
+ */
+ { "copy-paste",
+ CPU_P9,
+ ISA_V3_0B, USABLE_HV|USABLE_OS|USABLE_PR,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+
+ /*
+ * ISAv3.0B GSR SPR register
+ * POWER9 does not implement it
+ */
+ { "group-start-register",
+ 0,
+ ISA_V3_0B, USABLE_HV|USABLE_OS,
+ HV_NONE, OS_NONE,
+ -1, -1, -1,
+ NULL, },
+};
+
+static void add_cpu_feature_nodeps(struct dt_node *features, const struct cpu_feature *f)
+{
+ struct dt_node *feature;
+
+ feature = dt_new(features, f->name);
+ assert(feature);
+
+ dt_add_property_cells(feature, "isa", f->isa);
+ dt_add_property_cells(feature, "usable-privilege", f->usable_privilege);
+
+ if (f->usable_privilege & USABLE_HV) {
+ if (f->hv_support != HV_NONE) {
+ uint32_t s = 0;
+ if (f->hv_support == HV_HFSCR)
+ s |= HV_SUPPORT_HFSCR;
+
+ dt_add_property_cells(feature, "hv-support", s);
+ if (f->hfscr_bit_nr != -1)
+ dt_add_property_cells(feature, "hfscr-bit-nr", f->hfscr_bit_nr);
+ } else {
+ assert(f->hfscr_bit_nr == -1);
+ }
+ }
+
+ if (f->usable_privilege & USABLE_OS) {
+ if (f->os_support != OS_NONE) {
+ uint32_t s = 0;
+ if (f->os_support == OS_FSCR)
+ s |= OS_SUPPORT_FSCR;
+ dt_add_property_cells(feature, "os-support", s);
+ if (f->fscr_bit_nr != -1)
+ dt_add_property_cells(feature, "fscr-bit-nr", f->fscr_bit_nr);
+ } else {
+ assert(f->fscr_bit_nr == -1);
+ }
+ }
+
+ if (f->usable_privilege & USABLE_PR) {
+ if (f->hwcap_bit_nr != -1)
+ dt_add_property_cells(feature, "hwcap-bit-nr", f->hwcap_bit_nr);
+ }
+
+ if (f->dependencies_names)
+ dt_add_property(feature, "dependencies", NULL, 0);
+}
+
+static void add_cpufeatures_dependencies(struct dt_node *features)
+{
+ struct dt_node *feature;
+
+ dt_for_each_node(features, feature) {
+ const struct cpu_feature *f;
+ const char *deps_names;
+ struct dt_property *deps;
+ int nr_deps;
+ int i;
+
+ /* Find features with dependencies */
+
+ deps = __dt_find_property(feature, "dependencies");
+ if (!deps)
+ continue;
+
+ /* Find the matching cpu table */
+ for (i = 0; i < ARRAY_SIZE(cpu_features_table); i++) {
+ f = &cpu_features_table[i];
+ if (!strcmp(f->name, feature->name))
+ break;
+ }
+ assert(f->dependencies_names);
+
+ /*
+ * Count number of depended features and allocate space
+ * for phandles in the property.
+ */
+ deps_names = f->dependencies_names;
+ nr_deps = strcount(deps_names, " ") + 1;
+ dt_resize_property(&deps, nr_deps * sizeof(u32));
+ deps->len = nr_deps * sizeof(u32);
+
+ DBG("feature %s has %d dependencies (%s)\n", f->name, nr_deps, deps_names);
+ /*
+ * For each one, find the depended feature then advance to
+ * next name.
+ */
+ for (i = 0; i < nr_deps; i++) {
+ struct dt_node *dep;
+ int len;
+
+ if (nr_deps - i == 1)
+ len = strlen(deps_names);
+ else
+ len = strchr(deps_names, ' ') - deps_names;
+
+ dt_for_each_node(features, dep) {
+ if (!strncmp(deps_names, dep->name, len))
+ goto found_dep;
+ }
+
+ prlog(PR_ERR, "CPUFT: feature %s dependencies not found\n", f->name);
+ break;
+found_dep:
+ DBG(" %s found dep (%s)\n", f->name, dep->name);
+ dt_property_set_cell(deps, i, dep->phandle);
+
+ /* Advance over the name + delimiter */
+ deps_names += len + 1;
+ }
+ }
+}
+
+static void add_cpufeatures(struct dt_node *cpus,
+ uint32_t cpu_feature_isa, uint32_t cpu_feature_cpu)
+{
+ struct dt_node *features;
+ int i;
+
+ DBG("creating cpufeatures for cpu:%d isa:%d\n", cpu_feature_cpu, cpu_feature_isa);
+
+ features = dt_new(cpus, "features");
+ assert(features);
+
+ dt_add_property_cells(features, "isa", cpu_feature_isa);
+
+ dt_add_property_string(features, "device_type", "ibm,powerpc-cpu-features");
+
+ /* add without dependencies */
+ for (i = 0; i < ARRAY_SIZE(cpu_features_table); i++) {
+ const struct cpu_feature *f = &cpu_features_table[i];
+
+ if (f->cpus_supported & cpu_feature_cpu) {
+ DBG(" '%s'\n", f->name);
+ add_cpu_feature_nodeps(features, f);
+ }
+ }
+
+ /* dependency construction pass */
+ add_cpufeatures_dependencies(features);
+}
+
+void dt_add_cpufeatures(struct dt_node *root)
+{
+ int version;
+ uint32_t cpu_feature_isa = 0;
+ uint32_t cpu_feature_cpu = 0;
+ struct dt_node *cpus;
+
+ version = mfspr(SPR_PVR);
+ switch(PVR_TYPE(version)) {
+ case PVR_TYPE_P8:
+ case PVR_TYPE_P8E:
+ case PVR_TYPE_P8NVL:
+ cpu_feature_isa = ISA_V2_07B;
+ if (PVR_VERS_MAJ(version) == 1)
+ cpu_feature_cpu = CPU_P8_DD1;
+ else
+ cpu_feature_cpu = CPU_P8_DD2;
+ break;
+ case PVR_TYPE_P9:
+ cpu_feature_isa = ISA_V3_0B;
+ if (PVR_VERS_MAJ(version) == 1)
+ cpu_feature_cpu = CPU_P9_DD1;
+ else
+ cpu_feature_cpu = CPU_P9_DD2;
+ break;
+ default:
+ return;
+ }
+
+ cpus = dt_new_check(root, "cpus");
+
+ add_cpufeatures(cpus, cpu_feature_isa, cpu_feature_cpu);
+}
diff --git a/core/device.c b/core/device.c
index f3ee63fb..38a420eb 100644
--- a/core/device.c
+++ b/core/device.c
@@ -598,6 +598,13 @@ u32 dt_property_get_cell(const struct dt_property *prop, u32 index)
return fdt32_to_cpu(((const u32 *)prop->prop)[index]);
}
+void dt_property_set_cell(struct dt_property *prop, u32 index, u32 val)
+{
+ assert(prop->len >= (index+1)*sizeof(u32));
+ /* Always aligned, so this works. */
+ ((u32 *)prop->prop)[index] = cpu_to_fdt32(val);
+}
+
/* First child of this node. */
struct dt_node *dt_first(const struct dt_node *root)
{
diff --git a/core/init.c b/core/init.c
index 6b8137c8..4d4bf651 100644
--- a/core/init.c
+++ b/core/init.c
@@ -790,6 +790,7 @@ void __noreturn __nomcount main_cpu_entry(const void *fdt)
} else {
dt_expand(fdt);
}
+ dt_add_cpufeatures(dt_root);
/* Now that we have a full devicetree, verify that we aren't on fire. */
per_thread_sanity_checks();
diff --git a/doc/device-tree/ibm,powerpc-cpu-features/binding.txt b/doc/device-tree/ibm,powerpc-cpu-features/binding.txt
new file mode 100644
index 00000000..a5270484
--- /dev/null
+++ b/doc/device-tree/ibm,powerpc-cpu-features/binding.txt
@@ -0,0 +1,226 @@
+ibm,powerpc-cpu-features binding
+================================
+
+This device tree binding describes CPU features available to software, with
+enablement, privilege, and compatibility metadata.
+
+More general description of design and implementation of this binding is
+found in design.txt, which also points to documentation of specific features.
+
+
+/cpus/ibm,powerpc-cpu-features node binding
+-------------------------------------------
+
+Node: ibm,powerpc-cpu-features
+
+Description: Container of CPU feature nodes.
+
+The node name must be "ibm,powerpc-cpu-features" and it must be a child of the
+node "/cpus".
+
+The node is optional but should be provided by new OPAL firmware.
+
+Properties:
+
+- device_type
+ Usage: required
+ Value type: string
+ Definition: "cpu-features"
+
+- isa
+ Usage: required
+ Value type: <u32>
+ Definition:
+
+ isa that the CPU is currently running in. This provides instruction set
+ compatibility, less the individual feature nodes. For example, an ISA v3.0
+ implementation that lacks the "transactional-memory" cpufeature node
+ should not use transactional memory facilities.
+
+ Value corresponds to the "Power ISA Version" multiplied by 1000.
+ For example, <3000> corresponds to Version 3.0, <2070> to Version 2.07.
+ The minor digit is available for revisions.
+
+/cpus/ibm,powerpc-cpu-features/example-feature node bindings
+----------------------------------------------------------------
+
+Each child node of cpu-features represents a CPU feature / capability.
+
+Node: A string describing an architected CPU feature, e.g., "floating-point".
+
+Description: A feature or capability supported by the CPUs.
+
+The name of the node is a human readable string that forms the interface
+used to describe features to software. Features are currently documented
+in the code where they are implemented in skiboot/core/cpufeatures.c
+
+Presence of the node indicates the feature is available.
+
+Properties:
+
+- isa
+ Usage: required
+ Value type: <u32>
+ Definition:
+
+ First level of the Power ISA that the feature appears in.
+ Software should filter out features when constraining the
+ environment to a particular ISA version.
+
+ Value is defined similarly to /cpus/features/isa
+
+- usable-privilege
+ Usage: required
+ Value type: <u32> bit mask
+ Definition:
+ Bit numbers are LSB0
+ bit 0 - PR (problem state / user mode)
+ bit 1 - OS (privileged state)
+ bit 2 - HV (hypervisor state)
+ All other bits reserved and should be zero.
+
+ This property describes the privilege levels and/or software components
+ that can use the feature.
+
+ If bit 0 is set, then the hwcap-bit-nr property will exist.
+
+
+- hv-support
+ Usage: optional
+ Value type: <u32> bit mask
+ Definition:
+ Bit numbers are LSB0
+ bit 0 - HFSCR
+ All other bits reserved and should be zero.
+
+ This property describes the HV privilege support required to enable the
+ feature to lesser privilege levels. If the property does not exist then no
+ support is required.
+
+ If no bits are set, the hypervisor must have explicit/custom support for
+ this feature.
+
+ If the HFSCR bit is set, then the hfscr-bit-nr property will exist and
+ the feature may be enabled by setting this bit in the HFSCR register.
+
+
+- os-support
+ Usage: optional
+ Value type: <u32> bit mask
+ Definition:
+ Bit numbers are LSB0
+ bit 0 - FSCR
+ All other bits reserved and should be zero.
+
+ This property describes the OS privilege support required to enable the
+ feature to lesser privilege levels. If the property does not exist then no
+ support is required.
+
+ If no bits are set, the operating system must have explicit/custom support
+ for this feature.
+
+ If the FSCR bit is set, then the fscr-bit-nr property will exist and
+ the feature may be enabled by setting this bit in the FSCR register.
+
+
+- hfscr-bit-nr
+ Usage: optional
+ Value type: <u32>
+ Definition: HFSCR bit position (LSB0)
+
+ This property exists when the hv-support property HFSCR bit is set. This
+ property describes the bit number in the HFSCR register that the
+ hypervisor must set in order to enable this feature.
+
+ This property also exists if an HFSCR bit corresponds with this feature.
+ This makes CPU feature parsing slightly simpler.
+
+
+- fscr-bit-nr
+ Usage: optional
+ Value type: <u32>
+ Definition: FSCR bit position (LSB0)
+
+ This property exists when the os-support property FSCR bit is set. This
+ property describes the bit number in the FSCR register that the
+ operating system must set in order to enable this feature.
+
+ This property also exists if an FSCR bit corresponds with this feature.
+ This makes CPU feature parsing slightly simpler.
+
+
+- hwcap-bit-nr
+ Usage: optional
+ Value type: <u32>
+ Definition: Linux ELF AUX vector bit position (LSB0)
+
+ This property may exist when the usable-privilege property value has PR bit set.
+ This property describes the bit number that should be set in the ELF AUX
+ hardware capability vectors in order to advertise this feature to userspace.
+ Bits 0-31 correspond to bits 0-31 in AT_HWCAP vector. Bits 32-63 correspond
+ to 0-31 in AT_HWCAP2 vector, and so on. Missing AT_HWCAPx vectors implies
+ that the feature is not enabled or can not be advertised. Operating systems
+ may provide a number of unassigned hardware capability bits to allow for new
+ features to be advertised.
+
+ Some properties representing features created before this binding are
+ advertised to userspace without a one-to-one hwcap bit number may not specify
+ this bit. Operating system will handle those bits specifically. All new
+ features usable by userspace will have a hwcap-bit-nr property.
+
+
+- dependencies
+ Usage: optional
+ Value type: <prop-encoded-array>
+ Definition:
+
+ If this property exists then it is a list of phandles to cpu feature
+ nodes that must be enabled for this feature to be enabled.
+
+
+Example
+-------
+
+ /cpus/ibm,powerpc-cpu-features {
+ device_type = "ibm,powerpc-cpu-features";
+
+ isa = <3020>;
+
+ darn {
+ isa = <3000>;
+ usable-privilege = <1 | 2 | 4>;
+ hwcap-bit-nr = <xx>;
+ };
+
+ scv {
+ isa = <3000>;
+ usable-privilege = <1 | 2>;
+ os-support = <0>;
+ hwcap-bit-nr = <xx>;
+ };
+
+ stop {
+ isa = <3000>;
+ usable-privilege = <2 | 4>;
+ hv-support = <0>;
+ os-support = <0>;
+ };
+
+ vsx2 (hypothetical) {
+ isa = <3010>;
+ usable-privilege = <1 | 2 | 4>;
+ hv-support = <0>;
+ os-support = <0>;
+ hwcap-bit-nr = <xx>;
+ };
+
+ vsx2-newinsns {
+ isa = <3020>;
+ usable-privilege = <1 | 2 | 4>;
+ os-support = <1>;
+ fscr-bit-nr = <xx>;
+ hwcap-bit-nr = <xx>;
+ dependencies = <&vsx2>;
+ };
+
+ };
diff --git a/doc/device-tree/ibm,powerpc-cpu-features/design.txt b/doc/device-tree/ibm,powerpc-cpu-features/design.txt
new file mode 100644
index 00000000..490e80c5
--- /dev/null
+++ b/doc/device-tree/ibm,powerpc-cpu-features/design.txt
@@ -0,0 +1,157 @@
+ibm,powerpc-cpu-features binding
+================================
+
+The OPAL / skiboot code is the canonical location for this specification. All
+definitions of features, constant, bit positions, etc. must be documented here
+before being deployed in Linux. This is not presently part of LoPAPR.
+
+
+Interfaces
+----------
+This specification describes the /cpus/ibm,powerpc-cpu-features binding (the
+formal definition of binding can be found in binding.txt in this directory).
+
+This specification also involves the Linux ELF AUXV AT_HWCAP and AT_HWCAP2
+interfaces for PPC_FEATURE* bits. Allocation of new AT_HWCAP bits should be
+done in coordination with OPAL / skiboot, Linux, and glibc projects.
+
+The binding is passed to the hypervisor by firmware. The hypervisor may
+build a subset with unsupported/disabled features and hypervisor specifics
+removed, and pass that to a guest OS. The OS may advertise features to
+userspace.
+
+
+Background
+----------
+The cpu-features binding (subsequently "cpu-features") aims to provide an
+extensible metadata and protocol between different levels of system software
+(firmware, hypervisor, OS/guest, userspace) to advertise the CPU features
+available on the system. With each level able to shape the features available
+to the next.
+
+The binding specifies features common to all CPUs in the system. Heterogeneous
+CPU features are not supported at present (such could be added by providing
+additional cpu-features nodes and linking those to particular CPUs with
+additional features).
+
+There is no strict definition for what a CPU feature must be, but an
+architectural behaviour or performance characteristic (or group of related
+behaviours). They must be documented in skiboot/core/cpufeatures.c sufficiently
+precisely. More guidelines for feature definitions below.
+
+cpu-features is intended to provide fine grained control of CPU features at
+all levels of the stack (firmware, hypervisor, OS, userspace), with the
+ability for new CPU features to be used by some components without all
+components being upgraded (e.g., a new floating point instruction could be
+used by userspace math library without upgrading kernel and hypervisor).
+
+
+Overview
+--------
+
+The cpu-features node is created by firmware and passed to the hypervisor.
+The hypervisor may create cpu-features node to be passed to guest, based on
+the features that have been enabled, and policy decisions. Hypervisor specific
+features, and hypervisor bits and properties should not be advertised to
+guests. Guest OS may advertise features to userspace using another method
+(e.g., using AUXV vectors, userspace typically does not parse DT).
+
+When the cpu-features node is present, ibm,pa-features and individual feature
+properties (e.g., "ibm,vsx"), and cpu-version under the "cpu" compatible nodes
+can be ignored by the consumer. For compatibility, the provider must continue
+to provide those older properties and the consumer must not assume cpu-features
+exists.
+
+When this node exists, software may assume a base feature set which is ISA
+v2.07B (BookS) minus the explicit features listed in core/cpufeatures.c
+entries in this source tree.
+
+Each feature is advertised as a node underneath the cpu-features node, named
+with a human-readable string name that uniquely identifies specification of
+that capability.
+
+A feature node has a number of metadata properties describing privilege levels
+a feature may be used (HV, OS, PR/user), and information about how it is to
+be enabled and advertised to lesser privilege levels. Enabling means to make
+it available at a lesser privilege level, (how to enable a given feature
+for this privilege level is implicit: if the software know how to use a
+feature, it also knows how to enable it).
+
+Feature node properties:
+
+- "isa", the Power ISA version where this feature first became available.
+ In case of an implementation specific feature
+
+- "usable-privilege", a bitmask (HV, OS, PR/user) specifying which privilege
+ levels this feature may be used in.
+
+- "hv-support", a bitmask. If this exists, the hypervisor must do some work
+ to enable support for lesser privilege levels. Bits can be set in this mask
+ to specify prescription/recipes to enable the feature without custom code.
+ If no bits are set, no recipe exists and custom code must be used. HFSCR
+ register enable bit is the only such recipe currently.
+
+- "os-support", similar to hv-support. FSCR recipe.
+
+- Features may have additional properties associated, must be documented with
+ the feature.
+
+- Recipes may have additional properties associated. HFSCR recipe has
+ hfscr-bit-nr, and FSCR recipe has fscr-bit-nr.
+
+- "dependencies" array of phandles. If this exists, it links to the
+ features that must be enabled in order for this feature to be enabled.
+
+- "hwcap-bit-nr" if it exists provides a Linux ELF AUXV HWCAP bit number that
+ can be used to advertise this feature to userspace.
+
+Together, these compatibility, support, and dependencies properties allow
+unknown features to be enabled and advertised to lesser privilege levels
+(when possible).
+
+All bits not defined in usable, support masks must be 0, and should be ignored
+by consumers. This allows extensibility to add new privilege levels and new
+recipes. Unknown properties should also be ignored. This allows extensibility
+for additional methods and metadata for enablement and advertisement.
+
+The policy for seleting and configuring which features to advertise and use
+is left for implementations.
+
+
+Guidelines for defining features
+--------------------------------
+
+As a rough guide, features should be based on functional groups of changes
+to the ISA, or related performance characteristics.
+
+Grouping should be made by one or a combination of those that:
+- Share common enablement requirements (e.g., share particular registers or
+ firmware setup requirements).
+- Share common usage patterns (e..g, likely to be used together).
+- Are implemented with a particular new hardware unit.
+- Are optional in the ISA.
+
+Granularity can be debated, but fine grained and encompassing is generally
+preferable. For example, memory management unit may be considered fundamental,
+but the MMU in POWER9 is very different and in many ways incompatible from
+that in POWER8 even in hash mode.
+
+For example, "POWER9" would be too general, but a new feature for every
+instruction would be too specific. The "summary of changes" preface in Power
+ISA specification is a good starting point to give a guideline for granularity
+of the architected features.
+
+New features that offer additional or incompatible functionality beyond
+an existing feature may contain an ISA version postfix.
+
+Implementation specific behaviour should contain a CPU type postfix. E.g.,
+"machine-check-power9" gives exact MCE properties. If a future CPU has the same
+MCE architecture, it should define the same property. If it has a
+backward-compatible superset, it could additionally define
+"machine-check-newcpu".
+
+Features should be "positive" as much as possible. That is, the presence of
+a feature should indicate the presence of an additional CPU feature (e.g., a
+new instruction or register). This requires some anticipation and foresight
+for defining CPU features. "Negative" features may be unavoidable in some
+cases.
diff --git a/include/device.h b/include/device.h
index 5155daad..ca4dd0b0 100644
--- a/include/device.h
+++ b/include/device.h
@@ -125,6 +125,7 @@ void dt_check_del_prop(struct dt_node *node, const char *name);
/* Warning: moves *prop! */
void dt_resize_property(struct dt_property **prop, size_t len);
+void dt_property_set_cell(struct dt_property *prop, u32 index, u32 val);
u32 dt_property_get_cell(const struct dt_property *prop, u32 index);
/* First child of this node. */
diff --git a/include/skiboot.h b/include/skiboot.h
index 2b1f8a57..d2702983 100644
--- a/include/skiboot.h
+++ b/include/skiboot.h
@@ -184,6 +184,15 @@ extern void start_kernel_secondary(uint64_t entry) __noreturn;
/* Get description of machine from HDAT and create device-tree */
extern int parse_hdat(bool is_opal);
+struct dt_node;
+
+/* Add /cpus/features node for boot environment that passes an fdt */
+#ifdef DT_CPUFEATURES
+extern void dt_add_cpufeatures(struct dt_node *root);
+#else
+static inline void dt_add_cpufeatures(struct dt_node *root) { (void)root; }
+#endif
+
/* Root of device tree. */
extern struct dt_node *dt_root;
--
2.11.0
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