Re: [PATCH v2 3/9] xen/arm: Reserve FDT via early module mechanism

[Julien Grall <julien.grall@linaro.org>]

On 09/13/2013 12:40 PM, Ian Campbell wrote:
> This will stop us putting any heaps or relocating Xen itself over the FDT.
> 
> The devicetree will be copied to allocated memory in setup_mm and the original
> copy will be freed by discard_initial_modules.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> ---
>  xen/arch/arm/setup.c          |    3 ++-
>  xen/common/device_tree.c      |    9 ++++++++-
>  xen/include/xen/device_tree.h |   11 ++++++-----
>  3 files changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 1ba2eb3..ab3d9aa 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -510,9 +510,10 @@ void __init start_xen(unsigned long boot_phys_offset,
>  
>      smp_clear_cpu_maps();
>  
> +    /* This is mapped by head.S */
>      device_tree_flattened = (void *)BOOT_MISC_VIRT_START
>          + (fdt_paddr & ((1 << SECOND_SHIFT) - 1));
> -    fdt_size = device_tree_early_init(device_tree_flattened);
> +    fdt_size = device_tree_early_init(device_tree_flattened, fdt_paddr);
>  
>      cpus = smp_get_max_cpus();
>      cmdline_parse(device_tree_bootargs(device_tree_flattened));
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index c4f0f2c..9e0c224 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -510,14 +510,21 @@ static void __init early_print_info(void)
>   *
>   * Returns the size of the DTB.
>   */
> -size_t __init device_tree_early_init(const void *fdt)
> +size_t __init device_tree_early_init(const void *fdt, paddr_t paddr)
>  {
> +    struct dt_mb_module *mod;
>      int ret;
>  
>      ret = fdt_check_header(fdt);
>      if ( ret < 0 )
>          early_panic("No valid device tree\n");
>  
> +    mod = &early_info.modules.module[MOD_FDT];
> +    mod->start = paddr & PAGE_MASK;

Why do we need to align the flat device tree and not the other modules
(ie: initramfs, kernel,...)?
I looked at the memory code and it seems to handle non-aligned module.

> +    mod->size = (fdt_totalsize(fdt) + ~PAGE_MASK) & PAGE_MASK;

You can use PAGE_ALIGN(fdt_totalsize(fdt)).

> +
> +    early_info.modules.nr_mods = max(MOD_FDT, early_info.modules.nr_mods);
> +
>      device_tree_for_each_node((void *)fdt, early_scan_node, NULL);
>      early_print_info();
>  
> diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
> index 5cc1905..3e50383 100644
> --- a/xen/include/xen/device_tree.h
> +++ b/xen/include/xen/device_tree.h
> @@ -21,11 +21,12 @@
>  #define NR_MEM_BANKS 8
>  
>  #define MOD_XEN 0
> -#define MOD_KERNEL 1
> -#define MOD_INITRD 2
> -#define NR_MODULES 3
> +#define MOD_FDT 1
> +#define MOD_KERNEL 2
> +#define MOD_INITRD 3
> +#define NR_MODULES 4
>  
> -#define MOD_DISCARD_FIRST MOD_KERNEL
> +#define MOD_DISCARD_FIRST MOD_FDT
>  
>  struct membank {
>      paddr_t start;
> @@ -166,7 +167,7 @@ typedef int (*device_tree_node_func)(const void *fdt,
>  extern struct dt_early_info early_info;
>  extern void *device_tree_flattened;
>  
> -size_t __init device_tree_early_init(const void *fdt);
> +size_t __init device_tree_early_init(const void *fdt, paddr_t paddr);
>  
>  void __init device_tree_get_reg(const u32 **cell, u32 address_cells,
>                                  u32 size_cells,
> 


-- 
Julien Grall