diff options
Diffstat (limited to 'Documentation/arch/arm64')
| -rw-r--r-- | Documentation/arch/arm64/acpi_object_usage.rst | 81 | ||||
| -rw-r--r-- | Documentation/arch/arm64/arm-acpi.rst | 169 | ||||
| -rw-r--r-- | Documentation/arch/arm64/booting.rst | 32 | ||||
| -rw-r--r-- | Documentation/arch/arm64/cpu-feature-registers.rst | 2 | ||||
| -rw-r--r-- | Documentation/arch/arm64/elf_hwcaps.rst | 3 | ||||
| -rw-r--r-- | Documentation/arch/arm64/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/arch/arm64/kdump.rst | 92 | ||||
| -rw-r--r-- | Documentation/arch/arm64/memory.rst | 8 | ||||
| -rw-r--r-- | Documentation/arch/arm64/ptdump.rst | 96 | ||||
| -rw-r--r-- | Documentation/arch/arm64/silicon-errata.rst | 4 |
10 files changed, 419 insertions, 70 deletions
diff --git a/Documentation/arch/arm64/acpi_object_usage.rst b/Documentation/arch/arm64/acpi_object_usage.rst index 484ef9676653..1da22200fdf8 100644 --- a/Documentation/arch/arm64/acpi_object_usage.rst +++ b/Documentation/arch/arm64/acpi_object_usage.rst @@ -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** diff --git a/Documentation/arch/arm64/arm-acpi.rst b/Documentation/arch/arm64/arm-acpi.rst index 1636352756bb..94274a8d84cf 100644 --- a/Documentation/arch/arm64/arm-acpi.rst +++ b/Documentation/arch/arm64/arm-acpi.rst @@ -1,40 +1,41 @@ -===================== -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/arch/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. diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst index ffeccdd6bdac..b57776a68f15 100644 --- a/Documentation/arch/arm64/booting.rst +++ b/Documentation/arch/arm64/booting.rst @@ -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 diff --git a/Documentation/arch/arm64/cpu-feature-registers.rst b/Documentation/arch/arm64/cpu-feature-registers.rst index c7adc7897df6..4e4625f2455f 100644 --- a/Documentation/arch/arm64/cpu-feature-registers.rst +++ b/Documentation/arch/arm64/cpu-feature-registers.rst @@ -288,6 +288,8 @@ infrastructure: +------------------------------+---------+---------+ | Name | bits | visible | +------------------------------+---------+---------+ + | MOPS | [19-16] | y | + +------------------------------+---------+---------+ | RPRES | [7-4] | y | +------------------------------+---------+---------+ | WFXT | [3-0] | y | diff --git a/Documentation/arch/arm64/elf_hwcaps.rst b/Documentation/arch/arm64/elf_hwcaps.rst index 58a86d532228..8c8addb4194c 100644 --- a/Documentation/arch/arm64/elf_hwcaps.rst +++ b/Documentation/arch/arm64/elf_hwcaps.rst @@ -302,6 +302,9 @@ HWCAP2_SMEB16B16 HWCAP2_SMEF16F16 Functionality implied by ID_AA64SMFR0_EL1.F16F16 == 0b1 +HWCAP2_MOPS + Functionality implied by ID_AA64ISAR2_EL1.MOPS == 0b0001. + 4. Unused AT_HWCAP bits ----------------------- diff --git a/Documentation/arch/arm64/index.rst b/Documentation/arch/arm64/index.rst index ae21f8118830..d08e924204bf 100644 --- a/Documentation/arch/arm64/index.rst +++ b/Documentation/arch/arm64/index.rst @@ -15,11 +15,13 @@ ARM64 Architecture cpu-feature-registers elf_hwcaps hugetlbpage + kdump legacy_instructions memory memory-tagging-extension perf pointer-authentication + ptdump silicon-errata sme sve diff --git a/Documentation/arch/arm64/kdump.rst b/Documentation/arch/arm64/kdump.rst new file mode 100644 index 000000000000..56a89f45df28 --- /dev/null +++ b/Documentation/arch/arm64/kdump.rst @@ -0,0 +1,92 @@ +======================================= +crashkernel memory reservation on arm64 +======================================= + +Author: Baoquan He <bhe@redhat.com> + +Kdump mechanism is used to capture a corrupted kernel vmcore so that +it can be subsequently analyzed. In order to do this, a preliminarily +reserved memory is needed to pre-load the kdump kernel and boot such +kernel if corruption happens. + +That reserved memory for kdump is adapted to be able to minimally +accommodate the kdump kernel and the user space programs needed for the +vmcore collection. + +Kernel parameter +================ + +Through the kernel parameters below, memory can be reserved accordingly +during the early stage of the first kernel booting so that a continuous +large chunk of memomy can be found. The low memory reservation needs to +be considered if the crashkernel is reserved from the high memory area. + +- crashkernel=size@offset +- crashkernel=size +- crashkernel=size,high crashkernel=size,low + +Low memory and high memory +========================== + +For kdump reservations, low memory is the memory area under a specific +limit, usually decided by the accessible address bits of the DMA-capable +devices needed by the kdump kernel to run. Those devices not related to +vmcore dumping can be ignored. On arm64, the low memory upper bound is +not fixed: it is 1G on the RPi4 platform but 4G on most other systems. +On special kernels built with CONFIG_ZONE_(DMA|DMA32) disabled, the +whole system RAM is low memory. Outside of the low memory described +above, the rest of system RAM is considered high memory. + +Implementation +============== + +1) crashkernel=size@offset +-------------------------- + +The crashkernel memory must be reserved at the user-specified region or +fail if already occupied. + + +2) crashkernel=size +------------------- + +The crashkernel memory region will be reserved in any available position +according to the search order: + +Firstly, the kernel searches the low memory area for an available region +with the specified size. + +If searching for low memory fails, the kernel falls back to searching +the high memory area for an available region of the specified size. If +the reservation in high memory succeeds, a default size reservation in +the low memory will be done. Currently the default size is 128M, +sufficient for the low memory needs of the kdump kernel. + +Note: crashkernel=size is the recommended option for crashkernel kernel +reservations. The user would not need to know the system memory layout +for a specific platform. + +3) crashkernel=size,high crashkernel=size,low +--------------------------------------------- + +crashkernel=size,(high|low) are an important supplement to +crashkernel=size. They allows the user to specify how much memory needs +to be allocated from the high memory and low memory respectively. On +many systems the low memory is precious and crashkernel reservations +from this area should be kept to a minimum. + +To reserve memory for crashkernel=size,high, searching is first +attempted from the high memory region. If the reservation succeeds, the +low memory reservation will be done subsequently. + +If reservation from the high memory failed, the kernel falls back to +searching the low memory with the specified size in crashkernel=,high. +If it succeeds, no further reservation for low memory is needed. + +Notes: + +- If crashkernel=,low is not specified, the default low memory + reservation will be done automatically. + +- if crashkernel=0,low is specified, it means that the low memory + reservation is omitted intentionally. diff --git a/Documentation/arch/arm64/memory.rst b/Documentation/arch/arm64/memory.rst index 2a641ba7be3b..55a55f30eed8 100644 --- a/Documentation/arch/arm64/memory.rst +++ b/Documentation/arch/arm64/memory.rst @@ -33,8 +33,8 @@ AArch64 Linux memory layout with 4KB pages + 4 levels (48-bit):: 0000000000000000 0000ffffffffffff 256TB user ffff000000000000 ffff7fffffffffff 128TB kernel logical memory map [ffff600000000000 ffff7fffffffffff] 32TB [kasan shadow region] - ffff800000000000 ffff800007ffffff 128MB modules - ffff800008000000 fffffbffefffffff 124TB vmalloc + ffff800000000000 ffff80007fffffff 2GB modules + ffff800080000000 fffffbffefffffff 124TB vmalloc fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down) fffffbfffe000000 fffffbfffe7fffff 8MB [guard region] fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space @@ -50,8 +50,8 @@ AArch64 Linux memory layout with 64KB pages + 3 levels (52-bit with HW support): 0000000000000000 000fffffffffffff 4PB user fff0000000000000 ffff7fffffffffff ~4PB kernel logical memory map [fffd800000000000 ffff7fffffffffff] 512TB [kasan shadow region] - ffff800000000000 ffff800007ffffff 128MB modules - ffff800008000000 fffffbffefffffff 124TB vmalloc + ffff800000000000 ffff80007fffffff 2GB modules + ffff800080000000 fffffbffefffffff 124TB vmalloc fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down) fffffbfffe000000 fffffbfffe7fffff 8MB [guard region] fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst new file mode 100644 index 000000000000..5dcfc5d7cddf --- /dev/null +++ b/Documentation/arch/arm64/ptdump.rst @@ -0,0 +1,96 @@ +====================== +Kernel page table dump +====================== + +ptdump is a debugfs interface that provides a detailed dump of the +kernel page tables. It offers a comprehensive overview of the kernel +virtual memory layout as well as the attributes associated with the +various regions in a human-readable format. It is useful to dump the +kernel page tables to verify permissions and memory types. Examining the +page table entries and permissions helps identify potential security +vulnerabilities such as mappings with overly permissive access rights or +improper memory protections. + +Memory hotplug allows dynamic expansion or contraction of available +memory without requiring a system reboot. To maintain the consistency +and integrity of the memory management data structures, arm64 makes use +of the ``mem_hotplug_lock`` semaphore in write mode. Additionally, in +read mode, ``mem_hotplug_lock`` supports an efficient implementation of +``get_online_mems()`` and ``put_online_mems()``. These protect the +offlining of memory being accessed by the ptdump code. + +In order to dump the kernel page tables, enable the following +configurations and mount debugfs:: + + CONFIG_GENERIC_PTDUMP=y + CONFIG_PTDUMP_CORE=y + CONFIG_PTDUMP_DEBUGFS=y + + mount -t debugfs nodev /sys/kernel/debug + cat /sys/kernel/debug/kernel_page_tables + +On analysing the output of ``cat /sys/kernel/debug/kernel_page_tables`` +one can derive information about the virtual address range of the entry, +followed by size of the memory region covered by this entry, the +hierarchical structure of the page tables and finally the attributes +associated with each page. The page attributes provide information about +access permissions, execution capability, type of mapping such as leaf +level PTE or block level PGD, PMD and PUD, and access status of a page +within the kernel memory. Assessing these attributes can assist in +understanding the memory layout, access patterns and security +characteristics of the kernel pages. + +Kernel virtual memory layout example:: + + start address end address size attributes + +---------------------------------------------------------------------------------------+ + | ---[ Linear Mapping start ]---------------------------------------------------------- | + | .................. | + | 0xfff0000000000000-0xfff0000000210000 2112K PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED | + | 0xfff0000000210000-0xfff0000001c00000 26560K PTE ro NX SHD AF UXN MEM/NORMAL | + | .................. | + | ---[ Linear Mapping end ]------------------------------------------------------------ | + +---------------------------------------------------------------------------------------+ + | ---[ Modules start ]----------------------------------------------------------------- | + | .................. | + | 0xffff800000000000-0xffff800008000000 128M PTE | + | .................. | + | ---[ Modules end ]------------------------------------------------------------------- | + +---------------------------------------------------------------------------------------+ + | ---[ vmalloc() area ]---------------------------------------------------------------- | + | .................. | + | 0xffff800008010000-0xffff800008200000 1984K PTE ro x SHD AF UXN MEM/NORMAL | + | 0xffff800008200000-0xffff800008e00000 12M PTE ro x SHD AF CON UXN MEM/NORMAL | + | .................. | + | ---[ vmalloc() end ]----------------------------------------------------------------- | + +---------------------------------------------------------------------------------------+ + | ---[ Fixmap start ]------------------------------------------------------------------ | + | .................. | + | 0xfffffbfffdb80000-0xfffffbfffdb90000 64K PTE ro x SHD AF UXN MEM/NORMAL | + | 0xfffffbfffdb90000-0xfffffbfffdba0000 64K PTE ro NX SHD AF UXN MEM/NORMAL | + | .................. | + | ---[ Fixmap end ]-------------------------------------------------------------------- | + +---------------------------------------------------------------------------------------+ + | ---[ PCI I/O start ]----------------------------------------------------------------- | + | .................. | + | 0xfffffbfffe800000-0xfffffbffff800000 16M PTE | + | .................. | + | ---[ PCI I/O end ]------------------------------------------------------------------- | + +---------------------------------------------------------------------------------------+ + | ---[ vmemmap start ]----------------------------------------------------------------- | + | .................. | + | 0xfffffc0002000000-0xfffffc0002200000 2M PTE RW NX SHD AF UXN MEM/NORMAL | + | 0xfffffc0002200000-0xfffffc0020000000 478M PTE | + | .................. | + | ---[ vmemmap end ]------------------------------------------------------------------- | + +---------------------------------------------------------------------------------------+ + +``cat /sys/kernel/debug/kernel_page_tables`` output:: + + 0xfff0000001c00000-0xfff0000080000000 2020M PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED + 0xfff0000080000000-0xfff0000800000000 30G PMD + 0xfff0000800000000-0xfff0000800700000 7M PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED + 0xfff0000800700000-0xfff0000800710000 64K PTE ro NX SHD AF UXN MEM/NORMAL-TAGGED + 0xfff0000800710000-0xfff0000880000000 2089920K PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED + 0xfff0000880000000-0xfff0040000000000 4062G PMD + 0xfff0040000000000-0xffff800000000000 3964T PGD diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst index 9e311bc43e05..d6430ade349d 100644 --- a/Documentation/arch/arm64/silicon-errata.rst +++ b/Documentation/arch/arm64/silicon-errata.rst @@ -214,3 +214,7 @@ stable kernels. +----------------+-----------------+-----------------+-----------------------------+ | Fujitsu | A64FX | E#010001 | FUJITSU_ERRATUM_010001 | +----------------+-----------------+-----------------+-----------------------------+ + ++----------------+-----------------+-----------------+-----------------------------+ +| ASR | ASR8601 | #8601001 | N/A | ++----------------+-----------------+-----------------+-----------------------------+ |