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# SPDX-License-Identifier: GPL-2.0
config EARLY_PRINTK_USB
bool
config X86_VERBOSE_BOOTUP
bool "Enable verbose x86 bootup info messages"
default y
help
Enables the informational output from the decompression stage
(e.g. bzImage) of the boot. If you disable this you will still
see errors. Disable this if you want silent bootup.
config EARLY_PRINTK
bool "Early printk" if EXPERT
default y
help
Write kernel log output directly into the VGA buffer or to a serial
port.
This is useful for kernel debugging when your machine crashes very
early before the console code is initialized. For normal operation
it is not recommended because it looks ugly and doesn't cooperate
with klogd/syslogd or the X server. You should normally say N here,
unless you want to debug such a crash.
config EARLY_PRINTK_DBGP
bool "Early printk via EHCI debug port"
depends on EARLY_PRINTK && PCI
select EARLY_PRINTK_USB
help
Write kernel log output directly into the EHCI debug port.
This is useful for kernel debugging when your machine crashes very
early before the console code is initialized. For normal operation
it is not recommended because it looks ugly and doesn't cooperate
with klogd/syslogd or the X server. You should normally say N here,
unless you want to debug such a crash. You need usb debug device.
config EARLY_PRINTK_USB_XDBC
bool "Early printk via the xHCI debug port"
depends on EARLY_PRINTK && PCI
select EARLY_PRINTK_USB
help
Write kernel log output directly into the xHCI debug port.
One use for this feature is kernel debugging, for example when your
machine crashes very early before the regular console code is
initialized. Other uses include simpler, lockless logging instead of
a full-blown printk console driver + klogd.
For normal production environments this is normally not recommended,
because it doesn't feed events into klogd/syslogd and doesn't try to
print anything on the screen.
You should normally say N here, unless you want to debug early
crashes or need a very simple printk logging facility.
config EFI_PGT_DUMP
bool "Dump the EFI pagetable"
depends on EFI
select PTDUMP_CORE
help
Enable this if you want to dump the EFI page table before
enabling virtual mode. This can be used to debug miscellaneous
issues with the mapping of the EFI runtime regions into that
table.
config DEBUG_TLBFLUSH
bool "Set upper limit of TLB entries to flush one-by-one"
depends on DEBUG_KERNEL
help
X86-only for now.
This option allows the user to tune the amount of TLB entries the
kernel flushes one-by-one instead of doing a full TLB flush. In
certain situations, the former is cheaper. This is controlled by the
tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
to -1, the code flushes the whole TLB unconditionally. Otherwise,
for positive values of it, the kernel will use single TLB entry
invalidating instructions according to the following formula:
flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
If in doubt, say "N".
config IOMMU_DEBUG
bool "Enable IOMMU debugging"
depends on GART_IOMMU && DEBUG_KERNEL
depends on X86_64
help
Force the IOMMU to on even when you have less than 4GB of
memory and add debugging code. On overflow always panic. And
allow to enable IOMMU leak tracing. Can be disabled at boot
time with iommu=noforce. This will also enable scatter gather
list merging. Currently not recommended for production
code. When you use it make sure you have a big enough
IOMMU/AGP aperture. Most of the options enabled by this can
be set more finegrained using the iommu= command line
options. See Documentation/arch/x86/x86_64/boot-options.rst for more
details.
config IOMMU_LEAK
bool "IOMMU leak tracing"
depends on IOMMU_DEBUG && DMA_API_DEBUG
help
Add a simple leak tracer to the IOMMU code. This is useful when you
are debugging a buggy device driver that leaks IOMMU mappings.
config HAVE_MMIOTRACE_SUPPORT
def_bool y
config X86_DECODER_SELFTEST
bool "x86 instruction decoder selftest"
depends on DEBUG_KERNEL && INSTRUCTION_DECODER
depends on !COMPILE_TEST
help
Perform x86 instruction decoder selftests at build time.
This option is useful for checking the sanity of x86 instruction
decoder code.
If unsure, say "N".
choice
prompt "IO delay type"
default IO_DELAY_0X80
config IO_DELAY_0X80
bool "port 0x80 based port-IO delay [recommended]"
help
This is the traditional Linux IO delay used for in/out_p.
It is the most tested hence safest selection here.
config IO_DELAY_0XED
bool "port 0xed based port-IO delay"
help
Use port 0xed as the IO delay. This frees up port 0x80 which is
often used as a hardware-debug port.
config IO_DELAY_UDELAY
bool "udelay based port-IO delay"
help
Use udelay(2) as the IO delay method. This provides the delay
while not having any side-effect on the IO port space.
config IO_DELAY_NONE
bool "no port-IO delay"
help
No port-IO delay. Will break on old boxes that require port-IO
delay for certain operations. Should work on most new machines.
endchoice
config DEBUG_BOOT_PARAMS
bool "Debug boot parameters"
depends on DEBUG_KERNEL
depends on DEBUG_FS
help
This option will cause struct boot_params to be exported via debugfs.
config CPA_DEBUG
bool "CPA self-test code"
depends on DEBUG_KERNEL
help
Do change_page_attr() self-tests every 30 seconds.
config DEBUG_ENTRY
bool "Debug low-level entry code"
depends on DEBUG_KERNEL
help
This option enables sanity checks in x86's low-level entry code.
Some of these sanity checks may slow down kernel entries and
exits or otherwise impact performance.
If unsure, say N.
config DEBUG_NMI_SELFTEST
bool "NMI Selftest"
depends on DEBUG_KERNEL && X86_LOCAL_APIC
help
Enabling this option turns on a quick NMI selftest to verify
that the NMI behaves correctly.
This might help diagnose strange hangs that rely on NMI to
function properly.
If unsure, say N.
config DEBUG_IMR_SELFTEST
bool "Isolated Memory Region self test"
depends on INTEL_IMR
help
This option enables automated sanity testing of the IMR code.
Some simple tests are run to verify IMR bounds checking, alignment
and overlapping. This option is really only useful if you are
debugging an IMR memory map or are modifying the IMR code and want to
test your changes.
If unsure say N here.
config X86_DEBUG_FPU
bool "Debug the x86 FPU code"
depends on DEBUG_KERNEL
default y
help
If this option is enabled then there will be extra sanity
checks and (boot time) debug printouts added to the kernel.
This debugging adds some small amount of runtime overhead
to the kernel.
If unsure, say N.
config PUNIT_ATOM_DEBUG
tristate "ATOM Punit debug driver"
depends on PCI
select DEBUG_FS
select IOSF_MBI
help
This is a debug driver, which gets the power states
of all Punit North Complex devices. The power states of
each device is exposed as part of the debugfs interface.
The current power state can be read from
/sys/kernel/debug/punit_atom/dev_power_state
choice
prompt "Choose kernel unwinder"
default UNWINDER_ORC if X86_64
default UNWINDER_FRAME_POINTER if X86_32
help
This determines which method will be used for unwinding kernel stack
traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
livepatch, lockdep, and more.
config UNWINDER_ORC
bool "ORC unwinder"
depends on X86_64
select OBJTOOL
help
This option enables the ORC (Oops Rewind Capability) unwinder for
unwinding kernel stack traces. It uses a custom data format which is
a simplified version of the DWARF Call Frame Information standard.
This unwinder is more accurate across interrupt entry frames than the
frame pointer unwinder. It also enables a 5-10% performance
improvement across the entire kernel compared to frame pointers.
Enabling this option will increase the kernel's runtime memory usage
by roughly 2-4MB, depending on your kernel config.
config UNWINDER_FRAME_POINTER
bool "Frame pointer unwinder"
select ARCH_WANT_FRAME_POINTERS
select FRAME_POINTER
help
This option enables the frame pointer unwinder for unwinding kernel
stack traces.
The unwinder itself is fast and it uses less RAM than the ORC
unwinder, but the kernel text size will grow by ~3% and the kernel's
overall performance will degrade by roughly 5-10%.
config UNWINDER_GUESS
bool "Guess unwinder"
depends on EXPERT
depends on !STACKDEPOT
help
This option enables the "guess" unwinder for unwinding kernel stack
traces. It scans the stack and reports every kernel text address it
finds. Some of the addresses it reports may be incorrect.
While this option often produces false positives, it can still be
useful in many cases. Unlike the other unwinders, it has no runtime
overhead.
endchoice
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