Re: [Fastboot] [PATCH 03/03] kexec: Avoid overwriting the current pgd (V2, x86_64)

[Vivek Goyal <vgoyal@in.ibm.com>]

On Mon, May 29, 2006 at 05:40:32PM +0900, Magnus Damm wrote:
> 
> >However while I agree that you need to do this in assembly for
> >control I disagree that this code should be part of the
> >relocate_new_kernel function.
> >
> >Please move the code that uses page_table_a to a separate function,
> >that when it is done jumps to the control_code page.  Then you can
> >map this page both virtually and physically with a statically
> >allocated page table built a compile time.
> 
> This function, you write "uses page_table_a". Do you mean that the
> function allocates it? Or fills it in? Or maybe switches to it? Please
> clarify!
> 
> >This is a little simpler as you don't need to build this first
> >page table dynamically and a little clearer as you aren't trying to
> >get the control code page to serve two different functions.
> 
> But doesn't a static set of pages used for page_table_a just mean that
> you are wasting valuable unswappable kernel memory?

In your implementation, is control page swappable?

>Also, how can you
> be sure that the static pages are in a DMA-safe address range?
> 

Why would kernel setup DMA on statically allocated pages?    

Thanks
Vivek