frame_table initialisation

frame_table initialisation

[PUCCETTI Armand]

It is unclear for me how variable frame_table is initialised:

1. According to function __start_xen:
Variable frame_table is initialised by __start_xen -> init_frametable.

but

2. some lines before in __start_xen, this variable is referenced by 
function map_pages_to_xen -> virt_to_xen_l2 -> alloc_xen_pagetable -> 
mfn_to_page.
What should the value of frame_table be there?

Do I miss some pre-initialisation(s)?

Armand

Re: frame_table initialisation

[Keir Fraser]

On 26/2/07 14:45, "PUCCETTI Armand" <armand.puccetti@cea.fr> wrote:

> 2. some lines before in __start_xen, this variable is referenced by
> function map_pages_to_xen -> virt_to_xen_l2 -> alloc_xen_pagetable ->
> mfn_to_page.
> What should the value of frame_table be there?
> 
> Do I miss some pre-initialisation(s)?

The fact that frame_table is not initialised here (and hence will be NULL)
doesn't actually matter, since the result of mfn_to_page() is only actually
used as a value to page_to_mfn(). And page_to_mfn(mfn_to_page(m))==m for any
(constant) value of frame_table.

This code could be clearer I'll admit. It probably makes sense for
alloc_xen_pagetable to return an MFN rather than a page_info pointer.

 -- Keir