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

Wen Congyang
2012-06-12T06:22:10Z

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
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>