mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-22 21:47:04 +07:00
edce21216a
So the reserve_ebda_region() code has accumulated a number of problems over the years that make it really difficult to read and understand: - The calculation of 'lowmem' and 'ebda_addr' is an unnecessarily interleaved mess of first lowmem, then ebda_addr, then lowmem tweaks... - 'lowmem' here means 'super low mem' - i.e. 16-bit addressable memory. In other parts of the x86 code 'lowmem' means 32-bit addressable memory... This makes it super confusing to read. - It does not help at all that we have various memory range markers, half of which are 'start of range', half of which are 'end of range' - but this crucial property is not obvious in the naming at all ... gave me a headache trying to understand all this. - Also, the 'ebda_addr' name sucks: it highlights that it's an address (which is obvious, all values here are addresses!), while it does not highlight that it's the _start_ of the EBDA region ... - 'BIOS_LOWMEM_KILOBYTES' says a lot of things, except that this is the only value that is a pointer to a value, not a memory range address! - The function name itself is a misnomer: it says 'reserve_ebda_region()' while its main purpose is to reserve all the firmware ROM typically between 640K and 1MB, while the 'EBDA' part is only a small part of that ... - Likewise, the paravirt quirk flag name 'ebda_search' is misleading as well: this too should be about whether to reserve firmware areas in the paravirt case. - In fact thinking about this as 'end of RAM' is confusing: what this function *really* wants to reserve is firmware data and code areas! Once the thinking is inverted from a mixed 'ram' and 'reserved firmware area' notion to a pure 'reserved area' notion everything becomes a lot clearer. To improve all this rewrite the whole code (without changing the logic): - Firstly invert the naming from 'lowmem end' to 'BIOS reserved area start' and propagate this concept through all the variable names and constants. BIOS_RAM_SIZE_KB_PTR // was: BIOS_LOWMEM_KILOBYTES BIOS_START_MIN // was: INSANE_CUTOFF ebda_start // was: ebda_addr bios_start // was: lowmem BIOS_START_MAX // was: LOWMEM_CAP - Then clean up the name of the function itself by renaming it to reserve_bios_regions() and renaming the ::ebda_search paravirt flag to ::reserve_bios_regions. - Fix up all the comments (fix typos), harmonize and simplify their formulation and remove comments that become unnecessary due to the much better naming all around. Signed-off-by: Ingo Molnar <mingo@kernel.org>
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
/*
|
|
* linux/arch/i386/kernel/head32.c -- prepare to run common code
|
|
*
|
|
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
|
|
* Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com>
|
|
*/
|
|
|
|
#include <linux/init.h>
|
|
#include <linux/start_kernel.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/memblock.h>
|
|
|
|
#include <asm/setup.h>
|
|
#include <asm/sections.h>
|
|
#include <asm/e820.h>
|
|
#include <asm/page.h>
|
|
#include <asm/apic.h>
|
|
#include <asm/io_apic.h>
|
|
#include <asm/bios_ebda.h>
|
|
#include <asm/tlbflush.h>
|
|
#include <asm/bootparam_utils.h>
|
|
|
|
static void __init i386_default_early_setup(void)
|
|
{
|
|
/* Initialize 32bit specific setup functions */
|
|
x86_init.resources.reserve_resources = i386_reserve_resources;
|
|
x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
|
|
|
|
reserve_bios_regions();
|
|
}
|
|
|
|
asmlinkage __visible void __init i386_start_kernel(void)
|
|
{
|
|
cr4_init_shadow();
|
|
sanitize_boot_params(&boot_params);
|
|
|
|
x86_early_init_platform_quirks();
|
|
|
|
/* Call the subarch specific early setup function */
|
|
switch (boot_params.hdr.hardware_subarch) {
|
|
case X86_SUBARCH_INTEL_MID:
|
|
x86_intel_mid_early_setup();
|
|
break;
|
|
case X86_SUBARCH_CE4100:
|
|
x86_ce4100_early_setup();
|
|
break;
|
|
default:
|
|
i386_default_early_setup();
|
|
break;
|
|
}
|
|
|
|
start_kernel();
|
|
}
|