# 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/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//stack, livepatch, lockdep, and more. config UNWINDER_ORC bool "ORC unwinder" depends on X86_64 select STACK_VALIDATION 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