xref: /kernel/linux/linux-6.6/Documentation/ABI/testing/sysfs-firmware-efi-runtime-map

What:		/sys/firmware/efi/runtime-map/
Date:		December 2013
Contact:	Dave Young <dyoung@redhat.com>
Description:	Switching efi runtime services to virtual mode requires
		that all efi memory ranges which have the runtime attribute
		bit set to be mapped to virtual addresses.

		The efi runtime services can only be switched to virtual
		mode once without rebooting. The kexec kernel must maintain
		the same physical to virtual address mappings as the first
		kernel. The mappings are exported to sysfs so userspace tools
		can reassemble them and pass them into the kexec kernel.

		/sys/firmware/efi/runtime-map/ is the directory the kernel
		exports that information in.

		subdirectories are named with the number of the memory range::

			/sys/firmware/efi/runtime-map/0
			/sys/firmware/efi/runtime-map/1
			/sys/firmware/efi/runtime-map/2
			/sys/firmware/efi/runtime-map/3
			...

		Each subdirectory contains five files:

		=========   =========================================
		attribute   The attributes of the memory range.
		num_pages   The size of the memory range in pages.
		phys_addr   The physical address of the memory range.
		type        The type of the memory range.
		virt_addr   The virtual address of the memory range.
		=========   =========================================

		Above values are all hexadecimal numbers with the '0x' prefix.
Users:		Kexec