> + /* > + * reservedtop=size reserves a hole at the top of the kernel > + * address space which a hypervisor can load into later. > + * Needed for dynamically loaded hypervisors, so relocating > + * the fixmap can be done before paging initialization. > + * This hole must be a multiple of 4M. > + */ > + else if (!memcmp(from, "reservedtop=", 12)) { > + unsigned long reserved = memparse(from+12, &from); > + reserved &= ~0x3fffff; > + set_fixaddr_top(-reserved); > + } You need to add a dummy __setup for it, otherwise it will end up in init's environments or be warned about. Also it should be documented somewhere in Documentation -Andi