Re: [Qemu-devel] [PATCH for-1.4] hw/arm_boot: Align device tree to 4KB boundary, not page

[Blue Swirl]

Thanks, applied.

On Thu, Jan 24, 2013 at 7:02 PM, Peter Maydell <address@hidden> wrote:
> Align the device tree blob to a 4KB boundary, not to QEMU's
> idea of a page boundary -- the latter is the smallest possible
> page size for the architecture, which on ARM is 1KB.
> The documentation for Linux does not impose separation
> or alignment requirements on the device tree blob, but
> in practice some kernels will happily trash the entire
> page the initrd ends in after they have finished uncompressing
> the initrd. So 4KB-align the DTB to ensure it does not get
> trampled by these kernels.
>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> For 1.4 because this causes us problems booting 3.8 kernels
> with dtb, and the symptoms are highly confusing. I think this
> is a kernel bug, but it is one that is worth working around.
>
> In general I think code in hw/ that looks at TARGET_PAGE_*
> is probably a bit suspect...
>
>  hw/arm_boot.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/hw/arm_boot.c b/hw/arm_boot.c
> index 115f583..4065424 100644
> --- a/hw/arm_boot.c
> +++ b/hw/arm_boot.c
> @@ -441,9 +441,12 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
> *info)
>           * we point to the kernel args.
>           */
>          if (info->dtb_filename) {
> -            /* Place the DTB after the initrd in memory */
> -            hwaddr dtb_start = TARGET_PAGE_ALIGN(info->initrd_start +
> -                                                 initrd_size);
> +            /* Place the DTB after the initrd in memory. Note that some
> +             * kernels will trash anything in the 4K page the initrd
> +             * ends in, so make sure the DTB isn't caught up in that.
> +             */
> +            hwaddr dtb_start = QEMU_ALIGN_UP(info->initrd_start + 
> initrd_size,
> +                                             4096);
>              if (load_dtb(dtb_start, info)) {
>                  exit(1);
>              }
> --
> 1.7.9.5
>
>