Re: Trouble using update_va_mapping

[Mathieu Ropert <mro@adviseo.fr>]

Keir Fraser wrote:

>
> On 13 Feb 2006, at 16:06, Mathieu Ropert wrote:
>
>> i'm trying to run a very simple domU kernel on Xen/x86_64, and i'm 
>> getting some trouble with update_va_mapping(): when trying to remap 
>> some page table entry, i find the virtual address still pointing to 
>> the same machine address after the return of the hypercall.
>
>
> What machine page does 'cons' point at before update_va_mapping()? Is 
> it definitely a different page?
>
>  -- Keir
>
"cons" is a page in the domU kernel address space. I left a 4k blank 
(page aligned) after the kernel entry point for this purpose.
In terms of assembly code, it looks like something like this:

    .org 0x2000
    .globl console_page
    console_page:
    .fill 256, 8, 0

and then, cons = (struct xencons_interface *) &console_page in my C code.

That may sound stupid and/or lazy, but i wanted a valid virtual address 
easy, complexity will come after i fully understand the thing :)