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: Jan 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: Ingo Molnar <mingo@kernel.org>

Author: schnhrr

Documentation/admin-guide/kernel-parameters.txt

@@ -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

@@ -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);
 	}