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

H. Peter Anvin
2012-06-12T16:10:34Z

If what you care about is nodes, why not have an option to specify a map?

Wen Congyang <wency@cn.fujitsu.com> wrote:

>At 06/12/2012 05:15 AM, H. Peter Anvin Wrote:
>> On 06/11/2012 01:44 AM, Wen Congyang 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 fail to see what this does that cannot be done with the
>> since-long-existing memmap= option. Could you address why memmap=
>> doesn't match your needs?
>
>The memmap= option is very diffcult to use. The end user should know
>the memory
>map in the system. The end user can get the max address of NODE#0, but
>he
>may not know the memory map for NODE#0. If the end user give the wrong
>memory
>map, the kernel can not boot. For example: I add memmap=16G@0 in the
>kernel
>parameter, and the kernel cannot boot. The max_addr is more easier to
>use.
>
>Thanks
>Wen Congyang
>
>>
>> -hpa
>>
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