Re: [Xen-devel] [PATCH v2] ARM: parse separate DT properties for different commandlines

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 3 June 2013 14:43, Andre Przywara <andre.przywara@xxxxxxxxxxx> wrote:
> Currently we use the chosen/bootargs property as the Xen commandline
> and rely on xen,dom0-bootargs for Dom0. However this brings issues
> with bootloaders, which usually build bootargs by bootscripts for a
> Linux kernel - and not for the entirely different Xen hypervisor.
> Introduce a new possible device tree property "xen,xen-bootargs"
> explicitly for the Xen hypervisor and make the selection of which to
> use more fine grained:
> - If xen,xen-bootargs is present, it will be used for Xen.
> - If xen,dom0-bootargs is present, it will be used for Dom0.
> - If xen,xen-bootargs is _not_ present, but xen,dom0-bootargs is,
>   bootargs will be used for Xen. Like the current situation.
> - If no Xen specific properties are present, bootargs is for Dom0.
> - If xen,xen-bootargs is present, but xen,dom0-bootargs is missing,
>   bootargs will be used for Dom0.
>
> The aim is to allow common bootscripts to boot both Xen and native
> Linux with the same device tree blob. If needed, one could hard-code
> the Xen commandline into the DTB, leaving bootargs for Dom0 to be set
> by the (non Xen-aware) bootloader.
> I also have a simple patch for u-boot to transfer the content of the
> "xen_bootargs" environment variable into the xen,xen-bootargs dtb
> property.
> I will post the u-boot patch to their ML later.
>
> Changes from v1:
> - fix whitespace issues

Any news about this patch ? :)

> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxxx>
> ---
>  xen/arch/arm/domain_build.c | 13 ++++++++++---
>  xen/common/device_tree.c    |  7 ++++++-
>  2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index b92c64b..5809489 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -139,6 +139,7 @@ static int write_properties(struct domain *d, struct 
> kernel_info *kinfo,
>                              u32 address_cells, u32 size_cells)
>  {
>      const char *bootargs = NULL;
> +    int had_dom0_bootargs = 0;
>      int prop;
>
>      if ( early_info.modules.nr_mods >= 1 &&
> @@ -169,11 +170,17 @@ static int write_properties(struct domain *d, struct 
> kernel_info *kinfo,
>           */
>          if ( device_tree_node_matches(fdt, node, "chosen") )
>          {
> -            if ( strcmp(prop_name, "bootargs") == 0 )
> +            if ( strcmp(prop_name, "xen,xen-bootargs") == 0 )
> +                continue;
> +            if ( strcmp(prop_name, "xen,dom0-bootargs") == 0 )
> +            {
> +                had_dom0_bootargs = 1;
> +                bootargs = prop_data;

Here, you overwrite the previous "bootargs". This variable is set if
the module node contains "bootargs" property
(see process_multiboot_node in common/device_tree.c)

Could you either:
    1) Remove the possibility to set the command line via the custom multiboot
    2) Check if "bootargs" was not set

I think nobody uses the custom multiboot with the command line. So the
first solution seems to be the best.

--
Julien Grall

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