[uml-devel] Regarding Virtual Memory Emulation in UML.

[uml-devel] Regarding Virtual Memory Emulation in UML.

[Krishnappa Abhijith-A21204]

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Hi,
        Regarding Virtual Memory Emulation in UML (TT mode).
UML will create a file of Physical mem size and it allocates memory to
UML process by mmap() ing it.
 
Also in Jeff's article I read that Kernel's text and Data are located in
the process address space....
Why the kernels text and data will be in UML Process address space ?
Normaly kernel is a seprate entity right ?
So basically process and kernel address space co-exist.. May I know why?
 
Thanks,
Abhi

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Re: [uml-devel] Regarding Virtual Memory Emulation in UML.

[Jeff Dike]

On Mon, Mar 19, 2007 at 11:13:11AM +0800, Krishnappa Abhijith-A21204 wrote:
>         Regarding Virtual Memory Emulation in UML (TT mode).
> UML will create a file of Physical mem size and it allocates memory to
> UML process by mmap() ing it.
>  
> Also in Jeff's article I read that Kernel's text and Data are located in
> the process address space....

In tt mode, yes.

> Why the kernels text and data will be in UML Process address space ?

Because there is (or at the time, seemed to be) no other way to change
address space mappings (mmap, munmap, mprotect) or to get page fault
information except to have the UML kernel in the same address space as
the process.

> Normaly kernel is a seprate entity right ?

Sure, but this is the same situation as on i386.  The host kernel
occupies the upper 1G of the process address space.

> So basically process and kernel address space co-exist.. May I know
why?

Because it works, but skas0 shows another way to make this work.

				Jeff

-- 
Work email - jdike at linux dot intel dot com

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