Messages in this thread | | | Subject | Re: [PATCH] MIPS: Refactor early_parse_mem() to fix mem= parameter | From | Youling Tang <> | Date | Fri, 25 Feb 2022 09:12:38 +0800 |
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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@loongson.cn> > --- > 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"); >
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