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Re: [Xen-devel] Trouble using update_va_mapping

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Mathieu Ropert <mro@xxxxxxxxxx>
  • Date: Mon, 13 Feb 2006 18:07:52 +0100
  • Delivery-date: Tue, 14 Feb 2006 16:29:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

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
   .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 :)

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