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

Wen Congyang
2012-06-12T06:25:43Z

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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