Commit 9ea77bdb authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, bios: Make the x86 early memory reservation a kernel option 



Add a kernel command-line option so the x86 early memory reservation
size can be adjusted at runtime instead of only at compile time.

Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
LKML-Reference: <tip-d0cd7425@git.kernel.org>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent d0cd7425

Documentation/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -2150,6 +2150,11 @@ and is between 256 and 4096 characters. It is defined in the file 
			Reserves a hole at the top of the kernel virtual

			address space.



	reservelow=	[X86]

			Format: nn[K]

			Set the amount of memory to reserve for BIOS at

			the bottom of the address space.



	reset_devices	[KNL] Force drivers to reset the underlying device

			during initialization.

arch/x86/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -1326,7 +1326,7 @@ config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK 
	  Set whether the default state of memory_corruption_check is

	  on or off.



config X86_LOW_RESERVE

config X86_RESERVE_LOW

	int "Amount of low memory, in kilobytes, to reserve for the BIOS"

	default 64

	range 4 640

arch/x86/kernel/setup.c

+26 −2
Original line number Diff line number Diff line
@@ -618,6 +618,8 @@ static __init void reserve_ibft_region(void) 
		reserve_early_overlap_ok(addr, addr + size, "ibft");

}



static unsigned reserve_low = CONFIG_X86_RESERVE_LOW << 10;



static void __init trim_bios_range(void)

{

	/*
@@ -627,9 +629,9 @@ static void __init trim_bios_range(void) 
	 *

	 * This typically reserves additional memory (64KiB by default)

	 * since some BIOSes are known to corrupt low memory.  See the

	 * Kconfig help text for X86_LOW_RESERVE.

	 * Kconfig help text for X86_RESERVE_LOW.

	 */

	e820_update_range(0, ALIGN(CONFIG_X86_LOW_RESERVE << 10, PAGE_SIZE),

	e820_update_range(0, ALIGN(reserve_low, PAGE_SIZE),

			  E820_RAM, E820_RESERVED);



	/*
@@ -641,6 +643,28 @@ static void __init trim_bios_range(void) 
	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);

}



static int __init parse_reservelow(char *p)

{

	unsigned long long size;



	if (!p)

		return -EINVAL;



	size = memparse(p, &p);



	if (size < 4096)

		size = 4096;



	if (size > 640*1024)

		size = 640*1024;



	reserve_low = size;



	return 0;

}



early_param("reservelow", parse_reservelow);



/*

 * Determine if we were loaded by an EFI loader.  If so, then we have also been

 * passed the efi memmap, systab, etc., so we should use these data structures

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