Re: [PATCH] xen: boot via i386_start_kernel to get early reservations

[Yinghai Lu]

On Sat, May 24, 2008 at 2:49 AM, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> Boot Xen via i386_start_kernel so that all the early reservations are
> made properly; without these, it will start using the kernel and
> pagetables as early heap memory, which is a bit suboptimal.
>
> One tricky part is that reserve_early() will just panic if any of the
> early reservations overlap any others.  When a Xen domain is built, it
> constructs the initial address space as:
>
>  kernel text+data+bss
>  initrd
>  initial pagetable
>
> Therefore, when reserving the pagetable (from &_end to
> init_pg_tables_end), it covers the whole initrd area.  If it then
> tries to reserve the initrd, it will panic because of the overlap.
>
> The simple fix here is to reserve INIT_PG_TABLE first, and then only
> reserve the ramdisk if it doesn't overlap with the previous
> reservations.  A better/more complex fix might be to make
> reserve_early() deal with overlapping reservations.
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> ---
...
> ===================================================================
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1264,5 +1264,5 @@ asmlinkage void __init xen_start_kernel(
>        }
>
>        /* Start the world */
> -       start_kernel();
> +       i386_start_kernel();
> }
..

need to do the same thing in arch/x86/lguest.c::lguest_init

YH
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