linux-kernel - Re: [PATCH] xen: boot via i386_start

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Date:	Sat, 24 May 2008 15:04:32 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Rusty Russell" <rusty@...tcorp.com.au>,
	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xen: boot via i386_start_kernel to get early reservations

On Sat, May 24, 2008 at 2:49 AM, Jeremy Fitzhardinge <jeremy@...p.org> 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@...rix.com>
> ---
...
> ===================================================================
> --- 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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