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 <[email protected]>
---
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;
}
@@ -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");
--
2.1.0
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 <[email protected]>
>> ---
>> 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");
>>
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 <[email protected]>
> ---
> 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");
>