MIPS: Fix incorrect mem=X@Y handling

Web:        https://git.kernel.org/torvalds/c/67a3ba25aa955198196f40b76b329b3ab9ad415a
Commit:     67a3ba25aa955198196f40b76b329b3ab9ad415a
Parent:     627f4a2bdf113ab88abc65cb505c89cbf615eae0
Refname:    refs/heads/master
Author:     Marcin Nowakowski <[email protected]>
AuthorDate: Thu Feb 1 12:37:21 2018 +0100
Committer:  James Hogan <[email protected]>
CommitDate: Tue Feb 13 13:14:41 2018 +0000

    MIPS: Fix incorrect mem=X@Y handling
    
    Commit 73fbc1eba7ff ("MIPS: fix mem=X@Y commandline processing") 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 <[email protected]>
    Signed-off-by: Marcin Nowakowski <[email protected]>
    Fixes: 73fbc1eba7ff ("MIPS: fix mem=X@Y commandline processing")
    Cc: Ralf Baechle <[email protected]>
    Cc: [email protected]
    Cc: <[email protected]> # v4.11+
    Tested-by: Mathieu Malaterre <[email protected]>
    Patchwork: https://patchwork.linux-mips.org/patch/18562/
    Signed-off-by: James Hogan <[email protected]>
---
 arch/mips/kernel/setup.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 85bc601e9a0d..5f8b0a9e30b3 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 = (phys_addr_t)ULLONG_MAX;
 	bool bootmap_valid = false;
 	int i;
 
@@ -395,7 +396,8 @@ static void __init bootmem_init(void)
 	max_low_pfn = 0;
 
 	/*
-	 * Find the highest page frame number we have available.
+	 * Find the highest page frame number we have available
+	 * and the lowest used RAM address
 	 */
 	for (i = 0; i < boot_mem_map.nr_map; i++) {
 		unsigned long start, end;
@@ -407,6 +409,8 @@ static void __init bootmem_init(void)
 		end = PFN_DOWN(boot_mem_map.map[i].addr
 				+ boot_mem_map.map[i].size);
 
+		ramstart = min(ramstart, boot_mem_map.map[i].addr);
+
 #ifndef CONFIG_HIGHMEM
 		/*
 		 * Skip highmem here so we get an accurate max_low_pfn if low
@@ -436,6 +440,13 @@ static void __init bootmem_init(void)
 		mapstart = max(reserved_end, start);
 	}
 
+	/*
+	 * Reserve any memory between the start of RAM and PHYS_OFFSET
+	 */
+	if (ramstart > PHYS_OFFSET)
+		add_memory_region(PHYS_OFFSET, ramstart - PHYS_OFFSET,
+				  BOOT_MEM_RESERVED);
+
 	if (min_low_pfn >= max_low_pfn)
 		panic("Incorrect memory mapping !!!");
 	if (min_low_pfn > ARCH_PFN_OFFSET) {
@@ -664,9 +675,6 @@ 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);
--
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