Hi, Tiezhu
On 02/24/2022 08:52 PM, Tiezhu Yang wrote:
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] Memory: 2991952K/3145728K available (...)
After login, the output of free command is consistent with the
above log.
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
arch/mips/kernel/setup.c | 25 ++++++++-----------------
1 file changed, 8 insertions(+), 17 deletions(-)
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index f979adf..2917412 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 %lldMB\n", memory_limit >> 20);
return 0;
After applying this patch, my guess is that the kdump operation will fail.
In the MIPS architecture, when the kdump operation is performed, a
"mem=YM@XM" parameter will be added to the capture kernel (added by
kexec-tools), indicating that the available memory range of the
capture kernel is [X, X+Y).
After the "mem" parameter is changed to the above, there will be only
a similar parsing function like "mem=3G", and the type like
"mem=128M@64M" cannot be correctly parsed.
Thanks,
Youling.
}
@@ -633,6 +621,9 @@ static void __init arch_mem_init(char **cmdline_p)
parse_early_param();
+ /* Limit the memory size via mem= command-line parameter */
+ memblock_enforce_memory_limit(memory_limit);
+
if (usermem)
pr_info("User-defined physical RAM map overwrite\n");
