On 02/25/2022 09:12 AM, Youling Tang wrote:
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.
Hi Youling, Don't worry, it is another issue, I will take that into account once this patch is applied. This commit is the first step to fix the issue about mem=limit, I think it is possible to support mem=limit@base and I will do that later. Thanks, Tiezhu
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");
