# SPDX-License-Identifier: GPL-2.0-only
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menu "EFI (Extensible Firmware Interface) Support"
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depends on EFI
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config EFI_VARS
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tristate "EFI Variable Support via sysfs"
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depends on EFI && (X86 || IA64)
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default n
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help
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If you say Y here, you are able to get EFI (Extensible Firmware
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Interface) variable information via sysfs. You may read,
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write, create, and destroy EFI variables through this interface.
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Note that this driver is only retained for compatibility with
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legacy users: new users should use the efivarfs filesystem
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instead.
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config EFI_ESRT
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bool
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depends on EFI && !IA64
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default y
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config EFI_VARS_PSTORE
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tristate "Register efivars backend for pstore"
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depends on PSTORE
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default y
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help
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Say Y here to enable use efivars as a backend to pstore. This
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will allow writing console messages, crash dumps, or anything
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else supported by pstore to EFI variables.
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config EFI_VARS_PSTORE_DEFAULT_DISABLE
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bool "Disable using efivars as a pstore backend by default"
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depends on EFI_VARS_PSTORE
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default n
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help
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Saying Y here will disable the use of efivars as a storage
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backend for pstore by default. This setting can be overridden
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using the efivars module's pstore_disable parameter.
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config EFI_RUNTIME_MAP
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bool "Export efi runtime maps to sysfs"
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depends on X86 && EFI && KEXEC_CORE
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default y
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help
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Export efi runtime memory maps to /sys/firmware/efi/runtime-map.
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That memory map is used for example by kexec to set up efi virtual
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mapping the 2nd kernel, but can also be used for debugging purposes.
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See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
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config EFI_FAKE_MEMMAP
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bool "Enable EFI fake memory map"
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depends on EFI && X86
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default n
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help
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Saying Y here will enable "efi_fake_mem" boot option.
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By specifying this parameter, you can add arbitrary attribute
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to specific memory range by updating original (firmware provided)
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EFI memmap.
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This is useful for debugging of EFI memmap related feature.
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e.g. Address Range Mirroring feature.
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config EFI_MAX_FAKE_MEM
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int "maximum allowable number of ranges in efi_fake_mem boot option"
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depends on EFI_FAKE_MEMMAP
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range 1 128
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default 8
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help
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Maximum allowable number of ranges in efi_fake_mem boot option.
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Ranges can be set up to this value using comma-separated list.
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The default value is 8.
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config EFI_SOFT_RESERVE
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bool "Reserve EFI Specific Purpose Memory"
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depends on EFI && EFI_STUB && ACPI_HMAT
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default ACPI_HMAT
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help
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On systems that have mixed performance classes of memory EFI
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may indicate specific purpose memory with an attribute (See
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EFI_MEMORY_SP in UEFI 2.8). A memory range tagged with this
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attribute may have unique performance characteristics compared
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to the system's general purpose "System RAM" pool. On the
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expectation that such memory has application specific usage,
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and its base EFI memory type is "conventional" answer Y to
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arrange for the kernel to reserve it as a "Soft Reserved"
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resource, and set aside for direct-access (device-dax) by
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default. The memory range can later be optionally assigned to
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the page allocator by system administrator policy via the
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device-dax kmem facility. Say N to have the kernel treat this
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memory as "System RAM" by default.
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If unsure, say Y.
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config EFI_PARAMS_FROM_FDT
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bool
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help
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Select this config option from the architecture Kconfig if
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the EFI runtime support gets system table address, memory
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map address, and other parameters from the device tree.
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config EFI_RUNTIME_WRAPPERS
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bool
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config EFI_GENERIC_STUB
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bool
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config EFI_ARMSTUB_DTB_LOADER
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bool "Enable the DTB loader"
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depends on EFI_GENERIC_STUB && !RISCV
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default y
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help
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Select this config option to add support for the dtb= command
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line parameter, allowing a device tree blob to be loaded into
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memory from the EFI System Partition by the stub.
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If the device tree is provided by the platform or by
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the bootloader this option may not be needed.
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But, for various development reasons and to maintain existing
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functionality for bootloaders that do not have such support
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this option is necessary.
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config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER
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bool "Enable the command line initrd loader" if !X86
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depends on EFI_STUB && (EFI_GENERIC_STUB || X86)
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default y
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depends on !RISCV
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help
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Select this config option to add support for the initrd= command
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line parameter, allowing an initrd that resides on the same volume
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as the kernel image to be loaded into memory.
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This method is deprecated.
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config EFI_BOOTLOADER_CONTROL
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tristate "EFI Bootloader Control"
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default n
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help
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This module installs a reboot hook, such that if reboot() is
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invoked with a string argument NNN, "NNN" is copied to the
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"LoaderEntryOneShot" EFI variable, to be read by the
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bootloader. If the string matches one of the boot labels
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defined in its configuration, the bootloader will boot once
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to that label. The "LoaderEntryRebootReason" EFI variable is
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set with the reboot reason: "reboot" or "shutdown". The
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bootloader reads this reboot reason and takes particular
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action according to its policy.
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config EFI_CAPSULE_LOADER
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tristate "EFI capsule loader"
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depends on EFI
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help
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This option exposes a loader interface "/dev/efi_capsule_loader" for
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users to load EFI capsules. This driver requires working runtime
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capsule support in the firmware, which many OEMs do not provide.
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Most users should say N.
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config EFI_CAPSULE_QUIRK_QUARK_CSH
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bool "Add support for Quark capsules with non-standard headers"
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depends on X86 && !64BIT
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select EFI_CAPSULE_LOADER
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default y
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help
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Add support for processing Quark X1000 EFI capsules, whose header
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layout deviates from the layout mandated by the UEFI specification.
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config EFI_TEST
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tristate "EFI Runtime Service Tests Support"
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depends on EFI
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default n
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help
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This driver uses the efi.<service> function pointers directly instead
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of going through the efivar API, because it is not trying to test the
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kernel subsystem, just for testing the UEFI runtime service
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interfaces which are provided by the firmware. This driver is used
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by the Firmware Test Suite (FWTS) for testing the UEFI runtime
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interfaces readiness of the firmware.
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Details for FWTS are available from:
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<https://wiki.ubuntu.com/FirmwareTestSuite>
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Say Y here to enable the runtime services support via /dev/efi_test.
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If unsure, say N.
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config APPLE_PROPERTIES
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bool "Apple Device Properties"
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depends on EFI_STUB && X86
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select EFI_DEV_PATH_PARSER
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select UCS2_STRING
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help
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Retrieve properties from EFI on Apple Macs and assign them to
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devices, allowing for improved support of Apple hardware.
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Properties that would otherwise be missing include the
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Thunderbolt Device ROM and GPU configuration data.
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If unsure, say Y if you have a Mac. Otherwise N.
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config RESET_ATTACK_MITIGATION
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bool "Reset memory attack mitigation"
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depends on EFI_STUB
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help
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Request that the firmware clear the contents of RAM after a reboot
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using the TCG Platform Reset Attack Mitigation specification. This
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protects against an attacker forcibly rebooting the system while it
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still contains secrets in RAM, booting another OS and extracting the
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secrets. This should only be enabled when userland is configured to
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clear the MemoryOverwriteRequest flag on clean shutdown after secrets
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have been evicted, since otherwise it will trigger even on clean
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reboots.
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config EFI_RCI2_TABLE
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bool "EFI Runtime Configuration Interface Table Version 2 Support"
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depends on X86 || COMPILE_TEST
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help
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Displays the content of the Runtime Configuration Interface
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Table version 2 on Dell EMC PowerEdge systems as a binary
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attribute 'rci2' under /sys/firmware/efi/tables directory.
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RCI2 table contains BIOS HII in XML format and is used to populate
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BIOS setup page in Dell EMC OpenManage Server Administrator tool.
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The BIOS setup page contains BIOS tokens which can be configured.
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Say Y here for Dell EMC PowerEdge systems.
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config EFI_DISABLE_PCI_DMA
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bool "Clear Busmaster bit on PCI bridges during ExitBootServices()"
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help
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Disable the busmaster bit in the control register on all PCI bridges
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while calling ExitBootServices() and passing control to the runtime
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kernel. System firmware may configure the IOMMU to prevent malicious
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PCI devices from being able to attack the OS via DMA. However, since
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firmware can't guarantee that the OS is IOMMU-aware, it will tear
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down IOMMU configuration when ExitBootServices() is called. This
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leaves a window between where a hostile device could still cause
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damage before Linux configures the IOMMU again.
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If you say Y here, the EFI stub will clear the busmaster bit on all
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PCI bridges before ExitBootServices() is called. This will prevent
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any malicious PCI devices from being able to perform DMA until the
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kernel reenables busmastering after configuring the IOMMU.
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This option will cause failures with some poorly behaved hardware
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and should not be enabled without testing. The kernel commandline
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options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma"
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may be used to override this option.
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endmenu
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config EFI_EMBEDDED_FIRMWARE
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bool
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depends on EFI
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select CRYPTO_LIB_SHA256
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config UEFI_CPER
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bool
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config UEFI_CPER_ARM
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bool
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depends on UEFI_CPER && ( ARM || ARM64 )
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default y
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config UEFI_CPER_X86
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bool
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depends on UEFI_CPER && X86
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default y
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config EFI_DEV_PATH_PARSER
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bool
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depends on ACPI
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default n
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config EFI_EARLYCON
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def_bool y
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depends on EFI && SERIAL_EARLYCON && !ARM && !IA64
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select FONT_SUPPORT
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select ARCH_USE_MEMREMAP_PROT
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config EFI_CUSTOM_SSDT_OVERLAYS
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bool "Load custom ACPI SSDT overlay from an EFI variable"
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depends on EFI && ACPI
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default ACPI_TABLE_UPGRADE
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help
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Allow loading of an ACPI SSDT overlay from an EFI variable specified
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by a kernel command line option.
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See Documentation/admin-guide/acpi/ssdt-overlays.rst for more
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information.
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