Commit 2605e80d authored by Linus Torvalds's avatar Linus Torvalds
Browse files
Pull arm64 updates from Catalin Marinas:
 "Notable features are user-space support for the memcpy/memset
  instructions and the permission indirection extension.

   - Support for the Armv8.9 Permission Indirection Extensions. While
     this feature doesn't add new functionality, it enables future
     support for Guarded Control Stacks (GCS) and Permission Overlays

   - User-space support for the Armv8.8 memcpy/memset instructions

   - arm64 perf: support the HiSilicon SoC uncore PMU, Arm CMN sysfs
     identifier, support for the NXP i.MX9 SoC DDRC PMU, fixes and
     cleanups

   - Removal of superfluous ISBs on context switch (following
     retrospective architecture tightening)

   - Decode the ISS2 register during faults for additional information
     to help with debugging

   - KPTI clean-up/simplification of the trampoline exit code

   - Addressing several -Wmissing-prototype warnings

   - Kselftest improvements for signal handling and ptrace

   - Fix TPIDR2_EL0 restoring on sigreturn

   - Clean-up, robustness improvements of the module allocation code

   - More sysreg conversions to the automatic register/bitfields
     generation

   - CPU capabilities handling cleanup

   - Arm documentation updates: ACPI, ptdump"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (124 commits)
  kselftest/arm64: Add a test case for TPIDR2 restore
  arm64/signal: Restore TPIDR2 register rather than memory state
  arm64: alternatives: make clean_dcache_range_nopatch() noinstr-safe
  Documentation/arm64: Add ptdump documentation
  arm64: hibernate: remove WARN_ON in save_processor_state
  kselftest/arm64: Log signal code and address for unexpected signals
  docs: perf: Fix warning from 'make htmldocs' in hisi-pmu.rst
  arm64/fpsimd: Exit streaming mode when flushing tasks
  docs: perf: Add new description for HiSilicon UC PMU
  drivers/perf: hisi: Add support for HiSilicon UC PMU driver
  drivers/perf: hisi: Add support for HiSilicon H60PA and PAv3 PMU driver
  perf: arm_cspmu: Add missing MODULE_DEVICE_TABLE
  perf/arm-cmn: Add sysfs identifier
  perf/arm-cmn: Revamp model detection
  perf/arm_dmc620: Add cpumask
  arm64: mm: fix VA-range sanity check
  arm64/mm: remove now-superfluous ISBs from TTBR writes
  Documentation/arm64: Update ACPI tables from BBR
  Documentation/arm64: Update references in arm-acpi
  Documentation/arm64: Update ARM and arch reference
  ...
parents 2b603cd5 abc17128
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+3 −0
Original line number Diff line number Diff line
@@ -429,6 +429,9 @@
	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
			Extension support

	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
			Set instructions support

	ataflop=	[HW,M68k]

	atarimouse=	[HW,MOUSE] Atari Mouse
+26 −14
Original line number Diff line number Diff line
@@ -56,14 +56,14 @@ Example usage of perf::
For HiSilicon uncore PMU v2 whose identifier is 0x30, the topology is the same
as PMU v1, but some new functions are added to the hardware.

(a) L3C PMU supports filtering by core/thread within the cluster which can be
1. L3C PMU supports filtering by core/thread within the cluster which can be
specified as a bitmap::

  $# perf stat -a -e hisi_sccl3_l3c0/config=0x02,tt_core=0x3/ sleep 5

This will only count the operations from core/thread 0 and 1 in this cluster.

(b) Tracetag allow the user to chose to count only read, write or atomic
2. Tracetag allow the user to chose to count only read, write or atomic
operations via the tt_req parameeter in perf. The default value counts all
operations. tt_req is 3bits, 3'b100 represents read operations, 3'b101
represents write operations, 3'b110 represents atomic store operations and
@@ -73,14 +73,16 @@ represents write operations, 3'b110 represents atomic store operations and

This will only count the read operations in this cluster.

(c) Datasrc allows the user to check where the data comes from. It is 5 bits.
3. Datasrc allows the user to check where the data comes from. It is 5 bits.
Some important codes are as follows:
5'b00001: comes from L3C in this die;
5'b01000: comes from L3C in the cross-die;
5'b01001: comes from L3C which is in another socket;
5'b01110: comes from the local DDR;
5'b01111: comes from the cross-die DDR;
5'b10000: comes from cross-socket DDR;

- 5'b00001: comes from L3C in this die;
- 5'b01000: comes from L3C in the cross-die;
- 5'b01001: comes from L3C which is in another socket;
- 5'b01110: comes from the local DDR;
- 5'b01111: comes from the cross-die DDR;
- 5'b10000: comes from cross-socket DDR;

etc, it is mainly helpful to find that the data source is nearest from the CPU
cores. If datasrc_cfg is used in the multi-chips, the datasrc_skt shall be
configured in perf command::
@@ -88,15 +90,25 @@ configured in perf command::
  $# perf stat -a -e hisi_sccl3_l3c0/config=0xb9,datasrc_cfg=0xE/,
  hisi_sccl3_l3c0/config=0xb9,datasrc_cfg=0xF/ sleep 5

(d)Some HiSilicon SoCs encapsulate multiple CPU and IO dies. Each CPU die
4. Some HiSilicon SoCs encapsulate multiple CPU and IO dies. Each CPU die
contains several Compute Clusters (CCLs). The I/O dies are called Super I/O
clusters (SICL) containing multiple I/O clusters (ICLs). Each CCL/ICL in the
SoC has a unique ID. Each ID is 11bits, include a 6-bit SCCL-ID and 5-bit
CCL/ICL-ID. For I/O die, the ICL-ID is followed by:
5'b00000: I/O_MGMT_ICL;
5'b00001: Network_ICL;
5'b00011: HAC_ICL;
5'b10000: PCIe_ICL;

- 5'b00000: I/O_MGMT_ICL;
- 5'b00001: Network_ICL;
- 5'b00011: HAC_ICL;
- 5'b10000: PCIe_ICL;

5. uring_channel: UC PMU events 0x47~0x59 supports filtering by tx request
uring channel. It is 2 bits. Some important codes are as follows:

- 2'b11: count the events which sent to the uring_ext (MATA) channel;
- 2'b01: is the same as 2'b11;
- 2'b10: count the events which sent to the uring (non-MATA) channel;
- 2'b00: default value, count the events which sent to the both uring and
  uring_ext channel;

Users could configure IDs to count data come from specific CCL/ICL, by setting
srcid_cmd & srcid_msk, and data desitined for specific CCL/ICL by setting
+76 −5
Original line number Diff line number Diff line
@@ -17,16 +17,37 @@ For ACPI on arm64, tables also fall into the following categories:

       -  Recommended: BERT, EINJ, ERST, HEST, PCCT, SSDT

       -  Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, IBFT,
          IORT, MCHI, MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT,
          STAO, TCPA, TPM2, UEFI, XENV
       -  Optional: AGDI, BGRT, CEDT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT,
          HMAT, IBFT, IORT, MCHI, MPAM, MPST, MSCT, NFIT, PMTT, PPTT, RASF, SBST,
          SDEI, SLIT, SPMI, SRAT, STAO, TCPA, TPM2, UEFI, XENV

       -  Not supported: BOOT, DBGP, DMAR, ETDT, HPET, IVRS, LPIT, MSDM, OEMx,
          PSDT, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
       -  Not supported: AEST, APMT, BOOT, DBGP, DMAR, ETDT, HPET, IVRS, LPIT,
          MSDM, OEMx, PDTT, PSDT, RAS2, RSDT, SLIC, WAET, WDAT, WDRT, WPBT

====== ========================================================================
Table  Usage for ARMv8 Linux
====== ========================================================================
AEST   Signature Reserved (signature == "AEST")

       **Arm Error Source Table**

       This table informs the OS of any error nodes in the system that are
       compliant with the Arm RAS architecture.

AGDI   Signature Reserved (signature == "AGDI")

       **Arm Generic diagnostic Dump and Reset Device Interface Table**

       This table describes a non-maskable event, that is used by the platform
       firmware, to request the OS to generate a diagnostic dump and reset the device.

APMT   Signature Reserved (signature == "APMT")

       **Arm Performance Monitoring Table**

       This table describes the properties of PMU support implmented by
       components in the system.

BERT   Section 18.3 (signature == "BERT")

       **Boot Error Record Table**
@@ -47,6 +68,13 @@ BGRT Section 5.2.22 (signature == "BGRT")
       Optional, not currently supported, with no real use-case for an
       ARM server.

CEDT   Signature Reserved (signature == "CEDT")

       **CXL Early Discovery Table**

       This table allows the OS to discover any CXL Host Bridges and the Host
       Bridge registers.

CPEP   Section 5.2.18 (signature == "CPEP")

       **Corrected Platform Error Polling table**
@@ -184,6 +212,15 @@ HEST Section 18.3.2 (signature == "HEST")
       Must be supplied if RAS support is provided by the platform.  It
       is recommended this table be supplied.

HMAT   Section 5.2.28 (signature == "HMAT")

       **Heterogeneous Memory Attribute Table**

       This table describes the memory attributes, such as memory side cache
       attributes and bandwidth and latency details, related to Memory Proximity
       Domains. The OS uses this information to optimize the system memory
       configuration.

HPET   Signature Reserved (signature == "HPET")

       **High Precision Event timer Table**
@@ -241,6 +278,13 @@ MCHI Signature Reserved (signature == "MCHI")

       Optional, not currently supported.

MPAM   Signature Reserved (signature == "MPAM")

       **Memory Partitioning And Monitoring table**

       This table allows the OS to discover the MPAM controls implemented by
       the subsystems.

MPST   Section 5.2.21 (signature == "MPST")

       **Memory Power State Table**
@@ -281,18 +325,39 @@ PCCT Section 14.1 (signature == "PCCT)
       Recommend for use on arm64; use of PCC is recommended when using CPPC
       to control performance and power for platform processors.

PDTT   Section 5.2.29 (signature == "PDTT")

       **Platform Debug Trigger Table**

       This table describes PCC channels used to gather debug logs of
       non-architectural features.


PMTT   Section 5.2.21.12 (signature == "PMTT")

       **Platform Memory Topology Table**

       Optional, not currently supported.

PPTT   Section 5.2.30 (signature == "PPTT")

       **Processor Properties Topology Table**

       This table provides the processor and cache topology.

PSDT   Section 5.2.11.3 (signature == "PSDT")

       **Persistent System Description Table**

       Obsolete table, will not be supported.

RAS2   Section 5.2.21 (signature == "RAS2")

       **RAS Features 2 table**

       This table provides interfaces for the RAS capabilities implemented in
       the platform.

RASF   Section 5.2.20 (signature == "RASF")

       **RAS Feature table**
@@ -318,6 +383,12 @@ SBST Section 5.2.14 (signature == "SBST")

       Optional, not currently supported.

SDEI   Signature Reserved (signature == "SDEI")

       **Software Delegated Exception Interface table**

       This table advertises the presence of the SDEI interface.

SLIC   Signature Reserved (signature == "SLIC")

       **Software LIcensing table**
+108 −61
Original line number Diff line number Diff line
=====================
ACPI on ARMv8 Servers
=====================

ACPI can be used for ARMv8 general purpose servers designed to follow
the ARM SBSA (Server Base System Architecture) [0] and SBBR (Server
Base Boot Requirements) [1] specifications.  Please note that the SBBR
can be retrieved simply by visiting [1], but the SBSA is currently only
available to those with an ARM login due to ARM IP licensing concerns.

The ARMv8 kernel implements the reduced hardware model of ACPI version
===================
ACPI on Arm systems
===================

ACPI can be used for Armv8 and Armv9 systems designed to follow
the BSA (Arm Base System Architecture) [0] and BBR (Arm
Base Boot Requirements) [1] specifications.  Both BSA and BBR are publicly
accessible documents.
Arm Servers, in addition to being BSA compliant, comply with a set
of rules defined in SBSA (Server Base System Architecture) [2].

The Arm kernel implements the reduced hardware model of ACPI version
5.1 or later.  Links to the specification and all external documents
it refers to are managed by the UEFI Forum.  The specification is
available at http://www.uefi.org/specifications and documents referenced
by the specification can be found via http://www.uefi.org/acpi.

If an ARMv8 system does not meet the requirements of the SBSA and SBBR,
If an Arm system does not meet the requirements of the BSA and BBR,
or cannot be described using the mechanisms defined in the required ACPI
specifications, then ACPI may not be a good fit for the hardware.

While the documents mentioned above set out the requirements for building
industry-standard ARMv8 servers, they also apply to more than one operating
industry-standard Arm systems, they also apply to more than one operating
system.  The purpose of this document is to describe the interaction between
ACPI and Linux only, on an ARMv8 system -- that is, what Linux expects of
ACPI and Linux only, on an Arm system -- that is, what Linux expects of
ACPI and what ACPI can expect of Linux.


Why ACPI on ARM?
Why ACPI on Arm?
----------------
Before examining the details of the interface between ACPI and Linux, it is
useful to understand why ACPI is being used.  Several technologies already
exist in Linux for describing non-enumerable hardware, after all.  In this
section we summarize a blog post [2] from Grant Likely that outlines the
reasoning behind ACPI on ARMv8 servers.  Actually, we snitch a good portion
section we summarize a blog post [3] from Grant Likely that outlines the
reasoning behind ACPI on Arm systems.  Actually, we snitch a good portion
of the summary text almost directly, to be honest.

The short form of the rationale for ACPI on ARM is:
The short form of the rationale for ACPI on Arm is:

-  ACPI’s byte code (AML) allows the platform to encode hardware behavior,
   while DT explicitly does not support this.  For hardware vendors, being
@@ -47,7 +48,7 @@ The short form of the rationale for ACPI on ARM is:

-  In the enterprise server environment, ACPI has established bindings (such
   as for RAS) which are currently used in production systems.  DT does not.
   Such bindings could be defined in DT at some point, but doing so means ARM
   Such bindings could be defined in DT at some point, but doing so means Arm
   and x86 would end up using completely different code paths in both firmware
   and the kernel.

@@ -108,7 +109,7 @@ recent version of the kernel.

Relationship with Device Tree
-----------------------------
ACPI support in drivers and subsystems for ARMv8 should never be mutually
ACPI support in drivers and subsystems for Arm should never be mutually
exclusive with DT support at compile time.

At boot time the kernel will only use one description method depending on
@@ -121,11 +122,11 @@ time).

Booting using ACPI tables
-------------------------
The only defined method for passing ACPI tables to the kernel on ARMv8
The only defined method for passing ACPI tables to the kernel on Arm
is via the UEFI system configuration table.  Just so it is explicit, this
means that ACPI is only supported on platforms that boot via UEFI.

When an ARMv8 system boots, it can either have DT information, ACPI tables,
When an Arm system boots, it can either have DT information, ACPI tables,
or in some very unusual cases, both.  If no command line parameters are used,
the kernel will try to use DT for device enumeration; if there is no DT
present, the kernel will try to use ACPI tables, but only if they are present.
@@ -169,7 +170,7 @@ hardware reduced mode must be set to zero.

For the ACPI core to operate properly, and in turn provide the information
the kernel needs to configure devices, it expects to find the following
tables (all section numbers refer to the ACPI 6.1 specification):
tables (all section numbers refer to the ACPI 6.5 specification):

    -  RSDP (Root System Description Pointer), section 5.2.5

@@ -184,20 +185,76 @@ tables (all section numbers refer to the ACPI 6.1 specification):

    -  GTDT (Generic Timer Description Table), section 5.2.24

    -  PPTT (Processor Properties Topology Table), section 5.2.30

    -  DBG2 (DeBuG port table 2), section 5.2.6, specifically Table 5-6.

    -  APMT (Arm Performance Monitoring unit Table), section 5.2.6, specifically Table 5-6.

    -  AGDI (Arm Generic diagnostic Dump and Reset Device Interface Table), section 5.2.6, specifically Table 5-6.

    -  If PCI is supported, the MCFG (Memory mapped ConFiGuration
       Table), section 5.2.6, specifically Table 5-31.
       Table), section 5.2.6, specifically Table 5-6.

    -  If booting without a console=<device> kernel parameter is
       supported, the SPCR (Serial Port Console Redirection table),
       section 5.2.6, specifically Table 5-31.
       section 5.2.6, specifically Table 5-6.

    -  If necessary to describe the I/O topology, SMMUs and GIC ITSs,
       the IORT (Input Output Remapping Table, section 5.2.6, specifically
       Table 5-31).
       Table 5-6).

    -  If NUMA is supported, the following tables are required:

       - SRAT (System Resource Affinity Table), section 5.2.16

       - SLIT (System Locality distance Information Table), section 5.2.17

    -  If NUMA is supported, and the system contains heterogeneous memory,
       the HMAT (Heterogeneous Memory Attribute Table), section 5.2.28.

    -  If the ACPI Platform Error Interfaces are required, the following
       tables are conditionally required:

       - BERT (Boot Error Record Table, section 18.3.1)

       - EINJ (Error INJection table, section 18.6.1)

       - ERST (Error Record Serialization Table, section 18.5)

       - HEST (Hardware Error Source Table, section 18.3.2)

       - SDEI (Software Delegated Exception Interface table, section 5.2.6,
         specifically Table 5-6)

       - AEST (Arm Error Source Table, section 5.2.6,
         specifically Table 5-6)

       - RAS2 (ACPI RAS2 feature table, section 5.2.21)

    -  If the system contains controllers using PCC channel, the
       PCCT (Platform Communications Channel Table), section 14.1

    -  If the system contains a controller to capture board-level system state,
       and communicates with the host via PCC, the PDTT (Platform Debug Trigger
       Table), section 5.2.29.

    -  If NVDIMM is supported, the NFIT (NVDIMM Firmware Interface Table), section 5.2.26

    -  If video framebuffer is present, the BGRT (Boot Graphics Resource Table), section 5.2.23

    -  If IPMI is implemented, the SPMI (Server Platform Management Interface),
       section 5.2.6, specifically Table 5-6.

    -  If the system contains a CXL Host Bridge, the CEDT (CXL Early Discovery
       Table), section 5.2.6, specifically Table 5-6.

    -  If the system supports MPAM, the MPAM (Memory Partitioning And Monitoring table), section 5.2.6,
       specifically Table 5-6.

    -  If the system lacks persistent storage, the IBFT (ISCSI Boot Firmware
       Table), section 5.2.6, specifically Table 5-6.

    -  If NUMA is supported, the SRAT (System Resource Affinity Table)
       and SLIT (System Locality distance Information Table), sections
       5.2.16 and 5.2.17, respectively.

If the above tables are not all present, the kernel may or may not be
able to boot properly since it may not be able to configure all of the
@@ -269,16 +326,14 @@ Drivers should look for device properties in the _DSD object ONLY; the _DSD
object is described in the ACPI specification section 6.2.5, but this only
describes how to define the structure of an object returned via _DSD, and
how specific data structures are defined by specific UUIDs.  Linux should
only use the _DSD Device Properties UUID [5]:
only use the _DSD Device Properties UUID [4]:

   - UUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301

   - https://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf

The UEFI Forum provides a mechanism for registering device properties [4]
so that they may be used across all operating systems supporting ACPI.
Device properties that have not been registered with the UEFI Forum should
not be used.
Common device properties can be registered by creating a pull request to [4] so
that they may be used across all operating systems supporting ACPI.
Device properties that have not been registered with the UEFI Forum can be used
but not as "uefi-" common properties.

Before creating new device properties, check to be sure that they have not
been defined before and either registered in the Linux kernel documentation
@@ -306,7 +361,7 @@ process.

Once registration and review have been completed, the kernel provides an
interface for looking up device properties in a manner independent of
whether DT or ACPI is being used.  This API should be used [6]; it can
whether DT or ACPI is being used.  This API should be used [5]; it can
eliminate some duplication of code paths in driver probing functions and
discourage divergence between DT bindings and ACPI device properties.

@@ -448,15 +503,15 @@ ASWG
----
The ACPI specification changes regularly.  During the year 2014, for instance,
version 5.1 was released and version 6.0 substantially completed, with most of
the changes being driven by ARM-specific requirements.  Proposed changes are
the changes being driven by Arm-specific requirements.  Proposed changes are
presented and discussed in the ASWG (ACPI Specification Working Group) which
is a part of the UEFI Forum.  The current version of the ACPI specification
is 6.1 release in January 2016.
is 6.5 release in August 2022.

Participation in this group is open to all UEFI members.  Please see
http://www.uefi.org/workinggroup for details on group membership.

It is the intent of the ARMv8 ACPI kernel code to follow the ACPI specification
It is the intent of the Arm ACPI kernel code to follow the ACPI specification
as closely as possible, and to only implement functionality that complies with
the released standards from UEFI ASWG.  As a practical matter, there will be
vendors that provide bad ACPI tables or violate the standards in some way.
@@ -470,12 +525,12 @@ likely be willing to assist in submitting ECRs.

Linux Code
----------
Individual items specific to Linux on ARM, contained in the Linux
Individual items specific to Linux on Arm, contained in the Linux
source code, are in the list that follows:

ACPI_OS_NAME
                       This macro defines the string to be returned when
                       an ACPI method invokes the _OS method.  On ARM64
                       an ACPI method invokes the _OS method.  On Arm
                       systems, this macro will be "Linux" by default.
                       The command line parameter acpi_os=<string>
                       can be used to set it to some other value.  The
@@ -490,31 +545,23 @@ Documentation/arm64/acpi_object_usage.rst.

References
----------
[0] http://silver.arm.com
    document ARM-DEN-0029, or newer:
    "Server Base System Architecture", version 2.3, dated 27 Mar 2014
[0] https://developer.arm.com/documentation/den0094/latest
    document Arm-DEN-0094: "Arm Base System Architecture", version 1.0C, dated 6 Oct 2022

[1] https://developer.arm.com/documentation/den0044/latest
    Document Arm-DEN-0044: "Arm Base Boot Requirements", version 2.0G, dated 15 Apr 2022

[1] http://infocenter.arm.com/help/topic/com.arm.doc.den0044a/Server_Base_Boot_Requirements.pdf
    Document ARM-DEN-0044A, or newer: "Server Base Boot Requirements, System
    Software on ARM Platforms", dated 16 Aug 2014
[2] https://developer.arm.com/documentation/den0029/latest
    Document Arm-DEN-0029: "Arm Server Base System Architecture", version 7.1, dated 06 Oct 2022

[2] http://www.secretlab.ca/archives/151,
[3] http://www.secretlab.ca/archives/151,
    10 Jan 2015, Copyright (c) 2015,
    Linaro Ltd., written by Grant Likely.

[3] AMD ACPI for Seattle platform documentation
    http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2012/10/Seattle_ACPI_Guide.pdf


[4] http://www.uefi.org/acpi
    please see the link for the "ACPI _DSD Device
    Property Registry Instructions"

[5] http://www.uefi.org/acpi
    please see the link for the "_DSD (Device
    Specific Data) Implementation Guide"
[4] _DSD (Device Specific Data) Implementation Guide
    https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.pdf

[6] Kernel code for the unified device
[5] Kernel code for the unified device
    property interface can be found in
    include/linux/property.h and drivers/base/property.c.

+32 −0
Original line number Diff line number Diff line
@@ -379,6 +379,38 @@ Before jumping into the kernel, the following conditions must be met:

    - SMCR_EL2.EZT0 (bit 30) must be initialised to 0b1.

  For CPUs with Memory Copy and Memory Set instructions (FEAT_MOPS):

  - If the kernel is entered at EL1 and EL2 is present:

    - HCRX_EL2.MSCEn (bit 11) must be initialised to 0b1.

  For CPUs with the Extended Translation Control Register feature (FEAT_TCR2):

  - If EL3 is present:

    - SCR_EL3.TCR2En (bit 43) must be initialised to 0b1.

 - If the kernel is entered at EL1 and EL2 is present:

    - HCRX_EL2.TCR2En (bit 14) must be initialised to 0b1.

  For CPUs with the Stage 1 Permission Indirection Extension feature (FEAT_S1PIE):

  - If EL3 is present:

    - SCR_EL3.PIEn (bit 45) must be initialised to 0b1.

  - If the kernel is entered at EL1 and EL2 is present:

    - HFGRTR_EL2.nPIR_EL1 (bit 58) must be initialised to 0b1.

    - HFGWTR_EL2.nPIR_EL1 (bit 58) must be initialised to 0b1.

    - HFGRTR_EL2.nPIRE0_EL1 (bit 57) must be initialised to 0b1.

    - HFGRWR_EL2.nPIRE0_EL1 (bit 57) must be initialised to 0b1.

The requirements described above for CPU mode, caches, MMUs, architected
timers, coherency and system registers apply to all CPUs.  All CPUs must
enter the kernel in the same exception level.  Where the values documented
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