[PATCH v2] MIPS: fix incorrect mem=X@Y handling

[Mathieu Malaterre <malat@debian.org>]

From: Marcin Nowakowski <marcin.nowakowski@mips.com>

Change 73fbc1eba7ff added a fix to ensure that the memory range between
PHYS_OFFSET and low memory address specified by mem= cmdline argument is
not later processed by free_all_bootmem.
This change was incorrect for systems where the commandline specifies
more than 1 mem argument, as it will cause all memory between
PHYS_OFFSET and each of the memory offsets to be marked as reserved,
which results in parts of the RAM marked as reserved (Creator CI20's
u-boot has a default commandline argument 'mem=256M@0x0
mem=768M@0x30000000').

Change the behaviour to ensure that only the range between PHYS_OFFSET
and the lowest start address of the memories is marked as protected.

This change also ensures that the range is marked protected even if it's
only defined through the devicetree and not only via commandline
arguments.

Reported-by: Mathieu Malaterre <mathieu.malaterre@gmail.com>
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@mips.com>
Fixes: 73fbc1eba7ff ("MIPS: fix mem=X@Y commandline processing")
Cc: <stable@vger.kernel.org> # v4.11
---
v2: Use updated email adress, add tag for stable.
 arch/mips/kernel/setup.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 702c678de116..f19d61224c71 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -375,6 +375,7 @@ static void __init bootmem_init(void)
 	unsigned long reserved_end;
 	unsigned long mapstart = ~0UL;
 	unsigned long bootmap_size;
+	phys_addr_t ramstart = ~0UL;
 	bool bootmap_valid = false;
 	int i;
 
@@ -395,6 +396,21 @@ static void __init bootmem_init(void)
 	max_low_pfn = 0;
 
 	/*
+	 * Reserve any memory between the start of RAM and PHYS_OFFSET
+	 */
+	for (i = 0; i < boot_mem_map.nr_map; i++) {
+		if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
+			continue;
+
+		ramstart = min(ramstart, boot_mem_map.map[i].addr);
+	}
+
+	if (ramstart > PHYS_OFFSET)
+		add_memory_region(PHYS_OFFSET, ramstart - PHYS_OFFSET,
+				  BOOT_MEM_RESERVED);
+
+
+	/*
 	 * Find the highest page frame number we have available.
 	 */
 	for (i = 0; i < boot_mem_map.nr_map; i++) {
@@ -664,9 +680,6 @@ static int __init early_parse_mem(char *p)
 
 	add_memory_region(start, size, BOOT_MEM_RAM);
 
-	if (start && start > PHYS_OFFSET)
-		add_memory_region(PHYS_OFFSET, start - PHYS_OFFSET,
-				BOOT_MEM_RESERVED);
 	return 0;
 }
 early_param("mem", early_parse_mem);
-- 
2.11.0