Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ef61f8a3 authored by Jan H. Schönherr's avatar Jan H. Schönherr Committed by Ingo Molnar
Browse files

x86/boot/e820: Implement a range manipulation operator 



Add a more versatile memmap= operator, which -- in addition to all the
things that were possible before -- allows you to:

- redeclare existing ranges -- before, you were limited to adding ranges;
- drop any range -- like a mem= for any location;
- use any e820 memory type -- not just some predefined ones.

The syntax is:

  memmap=<size>%<offset>-<oldtype>+<newtype>

Size and offset work as usual. The "-<oldtype>" and "+<newtype>" are
optional and their existence determine the behavior: The command
works on the specified range of memory limited to type <oldtype>
(if specified). This memory is then configured to show up as <newtype>.
If <newtype> is not specified, the memory is removed from the e820 map.

Signed-off-by: default avatarJan H. Schönherr <jschoenh@amazon.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180202231020.15608-1-jschoenh@amazon.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 672c0ae0

Documentation/admin-guide/kernel-parameters.txt

+9 −0
Original line number Diff line number Diff line
@@ -2237,6 +2237,15 @@ 
			The memory region may be marked as e820 type 12 (0xc)

			and is NVDIMM or ADR memory.



	memmap=<size>%<offset>-<oldtype>+<newtype>

			[KNL,ACPI] Convert memory within the specified region

			from <oldtype> to <newtype>. If "-<oldtype>" is left

			out, the whole region will be marked as <newtype>,

			even if previously unavailable. If "+<newtype>" is left

			out, matching memory will be removed. Types are

			specified as e820 types, e.g., 1 = RAM, 2 = reserved,

			3 = ACPI, 12 = PRAM.



	memory_corruption_check=0/1 [X86]

			Some BIOSes seem to corrupt the first 64k of

			memory when doing things like suspend/resume.

arch/x86/kernel/e820.c

+18 −0
Original line number Diff line number Diff line
@@ -924,6 +924,24 @@ static int __init parse_memmap_one(char *p) 
	} else if (*p == '!') {

		start_at = memparse(p+1, &p);

		e820__range_add(start_at, mem_size, E820_TYPE_PRAM);

	} else if (*p == '%') {

		enum e820_type from = 0, to = 0;



		start_at = memparse(p + 1, &p);

		if (*p == '-')

			from = simple_strtoull(p + 1, &p, 0);

		if (*p == '+')

			to = simple_strtoull(p + 1, &p, 0);

		if (*p != '\0')

			return -EINVAL;

		if (from && to)

			e820__range_update(start_at, mem_size, from, to);

		else if (to)

			e820__range_add(start_at, mem_size, to);

		else if (from)

			e820__range_remove(start_at, mem_size, from, 1);

		else

			e820__range_remove(start_at, mem_size, 0, 0);

	} else {

		e820__range_remove(mem_size, ULLONG_MAX - mem_size, E820_TYPE_RAM, 1);

	}