[PATCH v4 1/4] MIPS: Refactor early_parse_mem() to fix mem= parameter

Tiezhu Yang
2022-03-01T04:29:12Z

According to Documentation/admin-guide/kernel-parameters.txt,
the kernel command-line parameter mem= means "Force usage of
a specific amount of memory", but when add "mem=3G" to the
command-line, kernel boot hangs in sparse_init().

This commit is similar with the implementation of the other
archs such as arm64, powerpc and riscv, refactor the function
early_parse_mem() and then use memblock_enforce_memory_limit()
to limit the memory size.

With this patch, when add "mem=3G" to the command-line, the
kernel boots successfully, we can see the following messages:

[ 0.000000] Memory limited to 3072MB
...
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000200000-0x000000000effffff]
[ 0.000000] node 0: [mem 0x0000000090200000-0x00000000ffffffff]
[ 0.000000] node 0: [mem 0x0000000120000000-0x00000001613fffff]
...
[ 0.000000] Memory: 3005280K/3145728K available (...)

After login, the output of free command is consistent with the
above log.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
arch/mips/kernel/setup.c | 26 +++++++++-----------------
1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index f979adf..50396ba 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -339,27 +339,15 @@ static void __init bootmem_init(void)
#endif /* CONFIG_SGI_IP27 */

static int usermem __initdata;
+static phys_addr_t memory_limit;

static int __init early_parse_mem(char *p)
{
- phys_addr_t start, size;
-
- /*
- * If a user specifies memory size, we
- * blow away any automatically generated
- * size.
- */
- if (usermem == 0) {
- usermem = 1;
- memblock_remove(memblock_start_of_DRAM(),
- memblock_end_of_DRAM() - memblock_start_of_DRAM());
- }
- start = 0;
- size = memparse(p, &p);
- if (*p == '@')
- start = memparse(p + 1, &p);
+ if (!p)
+ return 1;

- memblock_add(start, size);
+ memory_limit = memparse(p, &p) & PAGE_MASK;
+ pr_notice("Memory limited to %lluMB\n", (u64)memory_limit >> 20);

return 0;
}
@@ -678,6 +666,10 @@ static void __init arch_mem_init(char **cmdline_p)
memblock_reserve(__pa_symbol(&__nosave_begin),
__pa_symbol(&__nosave_end) - __pa_symbol(&__nosave_begin));

+ /* Limit the memory. */
+ memblock_enforce_memory_limit(memory_limit);
+ memblock_allow_resize();
+
early_memtest(PFN_PHYS(ARCH_PFN_OFFSET), PFN_PHYS(max_low_pfn));
}

--
2.1.0