linux-kernel - [PATCH AUTOSEL 5.7 08/24] MIPS: Fix unable to reserve memory for Crash kernel

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Date:   Wed, 19 Aug 2020 20:01:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jinyang He <hejinyang@...ngson.cn>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sasha Levin <sashal@...nel.org>, linux-mips@...r.kernel.org
Subject: [PATCH AUTOSEL 5.7 08/24] MIPS: Fix unable to reserve memory for Crash kernel

From: Jinyang He <hejinyang@...ngson.cn>

[ Upstream commit b1ce9716f3b5ed3b49badf1f003b9e34b7ead0f9 ]

Use 0 as the align parameter in memblock_find_in_range() is
incorrect when we reserve memory for Crash kernel.

The environment as follows:
[    0.000000] MIPS: machine is loongson,loongson64c-4core-rs780e
...
[    1.951016]     crashkernel=64M@...M

The warning as follows:
[    0.000000] Invalid memory region reserved for crash kernel

And the iomem as follows:
00200000-0effffff : System RAM
  04000000-0484009f : Kernel code
  048400a0-04ad7fff : Kernel data
  04b40000-05c4c6bf : Kernel bss
1a000000-1bffffff : pci@...00000
...

The align parameter may be finally used by round_down() or round_up().
Like the following call tree:

mips-next: mm/memblock.c

memblock_find_in_range
└── memblock_find_in_range_node
    ├── __memblock_find_range_bottom_up
    │   └── round_up
    └── __memblock_find_range_top_down
        └── round_down
\#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
\#define round_down(x, y) ((x) & ~__round_mask(x, y))
\#define __round_mask(x, y) ((__typeof__(x))((y)-1))

The round_down(or round_up)'s second parameter must be a power of 2.
If the second parameter is 0, it both will return 0.

Use 1 as the parameter to fix the bug and the iomem as follows:
00200000-0effffff : System RAM
  04000000-0484009f : Kernel code
  048400a0-04ad7fff : Kernel data
  04b40000-05c4c6bf : Kernel bss
  08000000-0bffffff : Crash kernel
1a000000-1bffffff : pci@...00000
...

Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
Reviewed-by: Jiaxun Yang <jiaxun.yang@...goat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 573509e0f2d4e..3ace115740dd1 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -497,7 +497,7 @@ static void __init mips_parse_crashkernel(void)
 	if (ret != 0 || crash_size <= 0)
 		return;
 
-	if (!memblock_find_in_range(crash_base, crash_base + crash_size, crash_size, 0)) {
+	if (!memblock_find_in_range(crash_base, crash_base + crash_size, crash_size, 1)) {
 		pr_warn("Invalid memory region reserved for crash kernel\n");
 		return;
 	}
-- 
2.25.1