Describing Physical RAM Map to Linux

Describing Physical RAM Map to Linux

[h h]

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Hi,

I have a very basic question -- When describing physical memory to the kernel in 
prom_init(), should we describe the physical memory region where kernel is loaded or leave it out?  We are using add_memory_region() call to describe physical memory to the kernel.  If we do describe the memory region where kernel is loaded, how will kernel know not to use these pages for User processes?

We are using 2.6.16 on Cavium/Octeon based platform. 

Thanks,
JJ



 
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Re: Describing Physical RAM Map to Linux

[Ralf Baechle]

On Sat, Apr 07, 2007 at 02:59:15PM -0700, h h wrote:

> I have a very basic question -- When describing physical memory to the kernel in 
> prom_init(), should we describe the physical memory region where kernel is loaded or leave it out?  We are using add_memory_region() call to describe physical memory to the kernel.  If we do describe the memory region where kernel is loaded, how will kernel know not to use these pages for User processes?

The kernel does this automatically.

> We are using 2.6.16 on Cavium/Octeon based platform. 

Which atm are only supported by Cavium's proprietary version of Linux ...

  Ralf

Re: Describing Physical RAM Map to Linux

[h h]

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On Sat, Apr 07, 2007 at 02:59:15PM -0700, h h wrote:

> I have a very basic question -- When describing physical memory to the kernel 
> in prom_init(), should we describe the physical memory region where kernel is 
> loaded or leave it out?  We are using add_memory_region() call to describe 
> physical memory to the kernel.  If we do describe the memory region where 
> kernel is loaded, how will kernel know not to use these pages for User 
> processes?

Ralf wrote:
The kernel does this automatically.

---

Sorry I don't quite understand -- What does kernel do 
automatically?  
How does kernel automatically know how much RAM is 
installed?

If you mean kernel automatically reserves the memory
it is loaded in, my question is where is this being 
done? I am expecting calls to alloc_bootmem or 
reserve_bootmem with addresses for text/data/stack
regions of kernel, but I don't see them.

Any pointers would be appreciated.


Thanks,



       
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