# SPDX-License-Identifier: GPL-2.0
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config TRACE_IRQFLAGS_SUPPORT
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def_bool y
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config EARLY_PRINTK_USB
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bool
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config X86_VERBOSE_BOOTUP
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bool "Enable verbose x86 bootup info messages"
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default y
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---help---
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Enables the informational output from the decompression stage
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(e.g. bzImage) of the boot. If you disable this you will still
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see errors. Disable this if you want silent bootup.
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config EARLY_PRINTK
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bool "Early printk" if EXPERT
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default y
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---help---
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Write kernel log output directly into the VGA buffer or to a serial
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port.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. For normal operation
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it is not recommended because it looks ugly and doesn't cooperate
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with klogd/syslogd or the X server. You should normally say N here,
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unless you want to debug such a crash.
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config EARLY_PRINTK_DBGP
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bool "Early printk via EHCI debug port"
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depends on EARLY_PRINTK && PCI
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select EARLY_PRINTK_USB
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---help---
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Write kernel log output directly into the EHCI debug port.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. For normal operation
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it is not recommended because it looks ugly and doesn't cooperate
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with klogd/syslogd or the X server. You should normally say N here,
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unless you want to debug such a crash. You need usb debug device.
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config EARLY_PRINTK_EFI
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bool "Early printk via the EFI framebuffer"
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depends on EFI && EARLY_PRINTK
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select FONT_SUPPORT
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---help---
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Write kernel log output directly into the EFI framebuffer.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized.
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config EARLY_PRINTK_USB_XDBC
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bool "Early printk via the xHCI debug port"
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depends on EARLY_PRINTK && PCI
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select EARLY_PRINTK_USB
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---help---
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Write kernel log output directly into the xHCI debug port.
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One use for this feature is kernel debugging, for example when your
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machine crashes very early before the regular console code is
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initialized. Other uses include simpler, lockless logging instead of
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a full-blown printk console driver + klogd.
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For normal production environments this is normally not recommended,
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because it doesn't feed events into klogd/syslogd and doesn't try to
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print anything on the screen.
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You should normally say N here, unless you want to debug early
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crashes or need a very simple printk logging facility.
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config MCSAFE_TEST
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def_bool n
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config X86_PTDUMP_CORE
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def_bool n
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config X86_PTDUMP
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tristate "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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select DEBUG_FS
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select X86_PTDUMP_CORE
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---help---
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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If in doubt, say "N"
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config EFI_PGT_DUMP
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bool "Dump the EFI pagetable"
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depends on EFI
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select X86_PTDUMP_CORE
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---help---
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Enable this if you want to dump the EFI page table before
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enabling virtual mode. This can be used to debug miscellaneous
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issues with the mapping of the EFI runtime regions into that
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table.
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config DEBUG_WX
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bool "Warn on W+X mappings at boot"
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select X86_PTDUMP_CORE
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---help---
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Generate a warning if any W+X mappings are found at boot.
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This is useful for discovering cases where the kernel is leaving
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W+X mappings after applying NX, as such mappings are a security risk.
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Look for a message in dmesg output like this:
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x86/mm: Checked W+X mappings: passed, no W+X pages found.
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or like this, if the check failed:
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x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
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Note that even if the check fails, your kernel is possibly
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still fine, as W+X mappings are not a security hole in
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themselves, what they do is that they make the exploitation
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of other unfixed kernel bugs easier.
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There is no runtime or memory usage effect of this option
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once the kernel has booted up - it's a one time check.
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If in doubt, say "Y".
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config DOUBLEFAULT
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default y
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bool "Enable doublefault exception handler" if EXPERT
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---help---
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This option allows trapping of rare doublefault exceptions that
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would otherwise cause a system to silently reboot. Disabling this
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option saves about 4k and might cause you much additional grey
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hair.
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config DEBUG_TLBFLUSH
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bool "Set upper limit of TLB entries to flush one-by-one"
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depends on DEBUG_KERNEL
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---help---
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X86-only for now.
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This option allows the user to tune the amount of TLB entries the
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kernel flushes one-by-one instead of doing a full TLB flush. In
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certain situations, the former is cheaper. This is controlled by the
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tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
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to -1, the code flushes the whole TLB unconditionally. Otherwise,
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for positive values of it, the kernel will use single TLB entry
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invalidating instructions according to the following formula:
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flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
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If in doubt, say "N".
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config IOMMU_DEBUG
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bool "Enable IOMMU debugging"
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depends on GART_IOMMU && DEBUG_KERNEL
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depends on X86_64
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---help---
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Force the IOMMU to on even when you have less than 4GB of
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memory and add debugging code. On overflow always panic. And
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allow to enable IOMMU leak tracing. Can be disabled at boot
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time with iommu=noforce. This will also enable scatter gather
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list merging. Currently not recommended for production
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code. When you use it make sure you have a big enough
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IOMMU/AGP aperture. Most of the options enabled by this can
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be set more finegrained using the iommu= command line
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options. See Documentation/x86/x86_64/boot-options.txt for more
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details.
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config IOMMU_LEAK
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bool "IOMMU leak tracing"
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depends on IOMMU_DEBUG && DMA_API_DEBUG
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---help---
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Add a simple leak tracer to the IOMMU code. This is useful when you
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are debugging a buggy device driver that leaks IOMMU mappings.
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config HAVE_MMIOTRACE_SUPPORT
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def_bool y
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config X86_DECODER_SELFTEST
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bool "x86 instruction decoder selftest"
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depends on DEBUG_KERNEL && INSTRUCTION_DECODER
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depends on !COMPILE_TEST
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---help---
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Perform x86 instruction decoder selftests at build time.
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This option is useful for checking the sanity of x86 instruction
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decoder code.
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If unsure, say "N".
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#
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# IO delay types:
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#
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config IO_DELAY_TYPE_0X80
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int
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default "0"
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config IO_DELAY_TYPE_0XED
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int
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default "1"
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config IO_DELAY_TYPE_UDELAY
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int
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default "2"
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config IO_DELAY_TYPE_NONE
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int
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default "3"
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choice
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prompt "IO delay type"
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default IO_DELAY_0X80
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config IO_DELAY_0X80
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bool "port 0x80 based port-IO delay [recommended]"
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---help---
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This is the traditional Linux IO delay used for in/out_p.
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It is the most tested hence safest selection here.
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config IO_DELAY_0XED
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bool "port 0xed based port-IO delay"
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---help---
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Use port 0xed as the IO delay. This frees up port 0x80 which is
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often used as a hardware-debug port.
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config IO_DELAY_UDELAY
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bool "udelay based port-IO delay"
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---help---
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Use udelay(2) as the IO delay method. This provides the delay
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while not having any side-effect on the IO port space.
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config IO_DELAY_NONE
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bool "no port-IO delay"
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---help---
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No port-IO delay. Will break on old boxes that require port-IO
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delay for certain operations. Should work on most new machines.
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endchoice
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if IO_DELAY_0X80
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0X80
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endif
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if IO_DELAY_0XED
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0XED
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endif
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if IO_DELAY_UDELAY
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_UDELAY
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endif
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if IO_DELAY_NONE
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_NONE
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endif
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config DEBUG_BOOT_PARAMS
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bool "Debug boot parameters"
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depends on DEBUG_KERNEL
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depends on DEBUG_FS
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---help---
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This option will cause struct boot_params to be exported via debugfs.
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config CPA_DEBUG
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bool "CPA self-test code"
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depends on DEBUG_KERNEL
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---help---
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Do change_page_attr() self-tests every 30 seconds.
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config OPTIMIZE_INLINING
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bool "Allow gcc to uninline functions marked 'inline'"
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---help---
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This option determines if the kernel forces gcc to inline the functions
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developers have marked 'inline'. Doing so takes away freedom from gcc to
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do what it thinks is best, which is desirable for the gcc 3.x series of
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compilers. The gcc 4.x series have a rewritten inlining algorithm and
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enabling this option will generate a smaller kernel there. Hopefully
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this algorithm is so good that allowing gcc 4.x and above to make the
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decision will become the default in the future. Until then this option
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is there to test gcc for this.
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If unsure, say N.
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config DEBUG_ENTRY
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bool "Debug low-level entry code"
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depends on DEBUG_KERNEL
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---help---
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This option enables sanity checks in x86's low-level entry code.
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Some of these sanity checks may slow down kernel entries and
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exits or otherwise impact performance.
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If unsure, say N.
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config DEBUG_NMI_SELFTEST
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bool "NMI Selftest"
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depends on DEBUG_KERNEL && X86_LOCAL_APIC
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---help---
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Enabling this option turns on a quick NMI selftest to verify
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that the NMI behaves correctly.
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This might help diagnose strange hangs that rely on NMI to
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function properly.
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If unsure, say N.
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config DEBUG_IMR_SELFTEST
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bool "Isolated Memory Region self test"
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default n
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depends on INTEL_IMR
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---help---
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This option enables automated sanity testing of the IMR code.
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Some simple tests are run to verify IMR bounds checking, alignment
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and overlapping. This option is really only useful if you are
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debugging an IMR memory map or are modifying the IMR code and want to
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test your changes.
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If unsure say N here.
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config X86_DEBUG_FPU
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bool "Debug the x86 FPU code"
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depends on DEBUG_KERNEL
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default y
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---help---
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If this option is enabled then there will be extra sanity
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checks and (boot time) debug printouts added to the kernel.
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This debugging adds some small amount of runtime overhead
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to the kernel.
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If unsure, say N.
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config PUNIT_ATOM_DEBUG
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tristate "ATOM Punit debug driver"
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depends on PCI
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select DEBUG_FS
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select IOSF_MBI
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---help---
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This is a debug driver, which gets the power states
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of all Punit North Complex devices. The power states of
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each device is exposed as part of the debugfs interface.
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The current power state can be read from
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/sys/kernel/debug/punit_atom/dev_power_state
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choice
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prompt "Choose kernel unwinder"
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default UNWINDER_ORC if X86_64
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default UNWINDER_FRAME_POINTER if X86_32
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---help---
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This determines which method will be used for unwinding kernel stack
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traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
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livepatch, lockdep, and more.
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config UNWINDER_ORC
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bool "ORC unwinder"
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depends on X86_64
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select STACK_VALIDATION
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---help---
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This option enables the ORC (Oops Rewind Capability) unwinder for
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unwinding kernel stack traces. It uses a custom data format which is
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a simplified version of the DWARF Call Frame Information standard.
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This unwinder is more accurate across interrupt entry frames than the
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frame pointer unwinder. It also enables a 5-10% performance
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improvement across the entire kernel compared to frame pointers.
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Enabling this option will increase the kernel's runtime memory usage
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by roughly 2-4MB, depending on your kernel config.
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config UNWINDER_FRAME_POINTER
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bool "Frame pointer unwinder"
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select FRAME_POINTER
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---help---
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This option enables the frame pointer unwinder for unwinding kernel
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stack traces.
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The unwinder itself is fast and it uses less RAM than the ORC
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unwinder, but the kernel text size will grow by ~3% and the kernel's
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overall performance will degrade by roughly 5-10%.
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This option is recommended if you want to use the livepatch
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consistency model, as this is currently the only way to get a
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reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
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config UNWINDER_GUESS
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bool "Guess unwinder"
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depends on EXPERT
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depends on !STACKDEPOT
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---help---
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This option enables the "guess" unwinder for unwinding kernel stack
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traces. It scans the stack and reports every kernel text address it
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finds. Some of the addresses it reports may be incorrect.
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While this option often produces false positives, it can still be
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useful in many cases. Unlike the other unwinders, it has no runtime
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overhead.
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endchoice
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config FRAME_POINTER
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depends on !UNWINDER_ORC && !UNWINDER_GUESS
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bool
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