Re: [PATCH 1/2 v2] x86: add max_addr boot option

[Wen Congyang <wency@cn.fujitsu.com>]

At 06/12/2012 01:35 AM, Bjorn Helgaas Wrote:
> On Mon, Jun 11, 2012 at 1:44 AM, Wen Congyang <wency@cn.fujitsu.com> wrote:
>> Currently, the boot option max_addr is only supported on ia64 platform.
>> We also need it on x86 platform.
>> For example:
>> There are two nodes:
>>  NODE#0  address range 0x00000000 00000000 - 0x00010000 00000000
>>  NODE#1  address range 0x00010000 00000000 - 0x00020000 00000000
>> If we only want to use node0, we can specify the max_addr. The boot
>> option "mem=" can do the same thing now. But the boot option "mem="
>> means the total memory used by the system. If we tell the user
>> that the boot option "mem=" can do this, it will confuse the user.
>> So we need an new boot option "max_addr" on x86 platform.
> 
> I don't object to this patch (and thanks for tweaking the mem range printk).
> 
> I don't know what your use case is, but from a user interface
> perspective, the "max_addr=" option feels like a bit of a hack.  If
> you're trying to avoid use of other nodes, "max_addr" is an awkward
> way to do it.  It requires the user to know the physical address ->
> node mappings, and it doesn't affect the CPUs and I/O resources on
> other nodes.  You could implement a "numa_node=" or similar parameter
> that would allow you to ignore remote memory, CPUs, and I/O.

Currently, I only need to ignore the memory. If we need to ignore a node,
"numa_node=" or similar parameter is a better choice.

Thanks
Wen Congyang

> 
>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>> ---
>>  Documentation/kernel-parameters.txt |    2 +-
>>  arch/x86/kernel/e820.c              |   36 +++++++++++++++++++++++++++++++++++
>>  2 files changed, 37 insertions(+), 1 deletions(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index a92c5eb..034609d 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -1441,7 +1441,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>                         yeeloong laptop.
>>                        Example: machtype=lemote-yeeloong-2f-7inch
>>
>> -       max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
>> +       max_addr=nn[KMG]        [KNL,BOOT,ia64,X86] All physical memory greater
>>                        than or equal to this physical address is ignored.
>>
>>        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
>> index 4185797..cd07226 100644
>> --- a/arch/x86/kernel/e820.c
>> +++ b/arch/x86/kernel/e820.c
>> @@ -47,6 +47,7 @@ unsigned long pci_mem_start = 0xaeedbabe;
>>  #ifdef CONFIG_PCI
>>  EXPORT_SYMBOL(pci_mem_start);
>>  #endif
>> +static u64 max_addr = ~0ULL;
>>
>>  /*
>>  * This function checks if any part of the range <start,end> is mapped
>> @@ -119,6 +120,20 @@ static void __init __e820_add_region(struct e820map *e820x, u64 start, u64 size,
>>                return;
>>        }
>>
>> +       if (start >= max_addr) {
>> +               printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n",
>> +                      (unsigned long long)start,
>> +                      (unsigned long long)(start + size - 1));
>> +               return;
>> +       }
>> +
>> +       if (max_addr - start < size) {
>> +               printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n",
>> +                      (unsigned long long)max_addr,
>> +                      (unsigned long long)(start + size - 1));
>> +               size = max_addr - start;
>> +       }
>> +
>>        e820x->map[x].addr = start;
>>        e820x->map[x].size = size;
>>        e820x->map[x].type = type;
>> @@ -835,6 +850,22 @@ static int __init parse_memopt(char *p)
>>  }
>>  early_param("mem", parse_memopt);
>>
>> +static int __init parse_memmax_opt(char *p)
>> +{
>> +       char *oldp;
>> +
>> +       if (!p)
>> +               return -EINVAL;
>> +
>> +       oldp = p;
>> +       max_addr = memparse(p, &p);
>> +       if (p == oldp)
>> +               return -EINVAL;
>> +
>> +       return 0;
>> +}
>> +early_param("max_addr", parse_memmax_opt);
>> +
>>  static int __init parse_memmap_opt(char *p)
>>  {
>>        char *oldp;
>> @@ -881,6 +912,11 @@ early_param("memmap", parse_memmap_opt);
>>
>>  void __init finish_e820_parsing(void)
>>  {
>> +       if (max_addr != ~0ULL) {
>> +               userdef = 1;
>> +               e820_remove_range(max_addr, ULLONG_MAX - max_addr, E820_RAM, 1);
>> +       }
>> +
>>        if (userdef) {
>>                u32 nr = e820.nr_map;
>>
>> --
>> 1.7.1
>>
> --
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