linux-kernel - Re: [v2] powerpc: Force page alignment for initrd

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Message-Id: <initrd-reserve-alignment@mdm.bga.com>
Date:	Sat, 21 May 2011 05:36:27 -0500
From:	Milton Miller <miltonm@....com>
To:	Dave Carroll <dcarroll@...ekcorp.com>
Cc:	'Benjamin Herrenschmidt' <benh@...nel.crashing.org>,
	"Paul Mackerras" <paulus@...ba.org>,
	"LPPC" <linuxppc-dev@...ts.ozlabs.org>,
	"LKML" <linux-kernel@...r.kernel.org>
Subject: Re: [v2] powerpc: Force page alignment for initrd

On Fri, 20 May 2011 about 13:23:36 -0000, Dave Carroll wrote:
> When using 64K pages with a separate cpio rootfs, U-Boot will align
> the rootfs on a 4K page boundary. When the memory is reserved, and
> subsequent early memblock_alloc is called, it will allocate memory
> between the 64K page alignment and reserved memory. When the reserved
> memory is subsequently freed, it is done so by pages, causing the
> early memblock_alloc requests to be re-used, which in my case, caused
> the device-tree to be clobbered.
> 
> This patch forces initrd to be kernel page aligned, to match the
> mechanism used to free reserved memory.

Actually it is only forcing the memory reserved for the initrd (its
not moving the contents nor filling the extra space).

> 
> @@ -555,7 +555,8 @@ static void __init early_reserve_mem(void)
>  #ifdef CONFIG_BLK_DEV_INITRD
>         /* then reserve the initrd, if any */
>         if (initrd_start && (initrd_end > initrd_start))
> -               memblock_reserve(__pa(initrd_start), initrd_end - initrd_start);
> +               memblock_reserve(_ALIGN_DOWN(__pa(initrd_start), PAGE_SIZE),
> +                       PAGE_ALIGN(initrd_end) - _ALIGN_DOWN(initrd_start, PAGE_SIZE));

Please align up the end, then change free_initrd_mem (32 and 64 bit)
to do the same range extension.

Thanks,
milton
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