Linux Virtualization - Jun 2007 - Lguest

Hello Rusty,

I'have just started to read the code (and I'm not an expert kernel
programmer), but is this condition ok ?


(function setup_pagetables(), on file Documentation/lguest.c )

    /* Ideally we map all physical memory starting at page_offset.
     * However, if page_offset is 0xC0000000 we can only map 1G of physical
     * (0xC0000000 + 1G overflows). */

    if (mem > -page_offset)
        mapped_pages =3D mem/getpagesize();
    else
        mapped_pages =3D -page_offset/getpagesize();



Cheers

Matias
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On Thu, 2007-06-28 at 19:03 +0200, Matias Zabaljauregui
wrote:
> Hello Rusty, 
> 
> I'have just started to read the code (and I'm not an expert kernel
> programmer), but is this condition ok ?
> 
> 
> (function setup_pagetables(), on file Documentation/lguest.c )
> 
>     /* Ideally we map all physical memory starting at page_offset. 
>      * However, if page_offset is 0xC0000000 we can only map 1G of
> physical
>      * (0xC0000000 + 1G overflows). */
> 
>     if (mem > -page_offset)
>         mapped_pages = mem/getpagesize();
>     else
>         mapped_pages = -page_offset/getpagesize(); 
Hi Matias,

	I think so: these are unsigned values, so "-page_offset" is the
address
space available for kernel memory (usually 1G).  It's a little
strange-looking, I admit.

Hope that helps,
Rusty.