Re: [Xen-devel] [PATCH v6 08/15] x86/efi: create new early memory allocator

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Hi Julien,

On Thu, Sep 22, 2016 at 06:07:26PM +0100, Julien Grall wrote:

[...]

> >#ifndef CONFIG_ARM
> >/* Whole x86 ebmalloc stuff. */
> >...
> >#else
> >void __init free_ebmalloc_unused_mem(void)
> >{
> >}
> >#endif
> >
> >and then call free_ebmalloc_unused_mem() from e.g.
> >xen/arch/arm/setup.c:init_done(). Am I right?
>
> Bear in mind that the EFI loader on ARM is standalone. It cannot
> interact with Xen.
>
> The main goal of the EFI stub is to load the different images on the
> memory and then will jump at the same starting point as when Xen is
> loaded without EFI. So anything in bss will be zeroed.

AIUI, on ARM EFI we have following call sequence:
  - efi_start(),
  - efi_xen_start(),
  - real_start()
  - ...
  - el2() which zeroes BSS... ;-(((

We had the same situation on x86. So, we moved BSS init just before
efi_start() call and disabled later zero BSS if we are booted via EFI.
Could we do the same on ARM? As I can see Jan wish to use ebmalloc on
ARM too. Does it make sense for you?

Thank you for pointing this issue out.

Daniel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel