zephyr/arch/x86_64/Kconfig

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arch/x86_64: New architecture added This patch adds a x86_64 architecture and qemu_x86_64 board to Zephyr. Only the basic architecture support needed to run 64 bit code is added; no drivers are added, though a low-level console exists and is wired to printk(). The support is built on top of a "X86 underkernel" layer, which can be built in isolation as a unit test on a Linux host. Limitations: + Right now the SDK lacks an x86_64 toolchain. The build will fall back to a host toolchain if it finds no cross compiler defined, which is tested to work on gcc 8.2.1 right now. + No x87/SSE/AVX usage is allowed. This is a stronger limitation than other architectures where the instructions work from one thread even if the context switch code doesn't support it. We are passing -no-sse to prevent gcc from automatically generating SSE instructions for non-floating-point purposes, which has the side effect of changing the ABI. Future work to handle the FPU registers will need to be combined with an "application" ABI distinct from the kernel one (or just to require USERSPACE). + Paging is enabled (it has to be in long mode), but is a 1:1 mapping of all memory. No MMU/USERSPACE support yet. + We are building with -mno-red-zone for stack size reasons, but this is a valuable optimization. Enabling it requires automatic stack switching, which requires a TSS, which means it has to happen after MMU support. + The OS runs in 64 bit mode, but for compatibility reasons is compiled to the 32 bit "X32" ABI. So while the full 64 bit registers and instruction set are available, C pointers are 32 bits long and Zephyr is constrained to run in the bottom 4G of memory. Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
2018-08-20 03:24:48 +08:00
config ARCH
default "x86_64"
config XUK_DEBUG
bool "Debug logging at lowest level"
help
When true, enables debug logging from the XUK layer in very
early boot situations (including the 16 and 32 bit stub
code) on the first serial port (115200 8n1) and VGA text
console. Also wires that output stream to the printk()
function so it can be used before any console drivers are
initialized.
config XUK_APIC_TSC_SHIFT
int "Power-of-two divisor between TSC and APIC timer"
default 6
help
Configures the precision of the APIC timer as a bit shift of
the TSC frequency. High values "slow down" the tick rate of
the APIC timer and allow for longer timeouts at the expense
of precision.
config IRQ_OFFLOAD_VECTOR
int "Interrupt vector for irq_offload"
default 255
help
This is the interrupt vector to use for the self-directed
IPIs used to implement irq_offload(). Most apps will never
change this. It's configurable in case someone wants to
play with its priority.