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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-08-20 at 13:19 +0100, Julien Grall wrote:
> On 20 August 2013 13:09, Andre Przywara <andre.przywara@xxxxxxxxxx> wrote:
> > On 07/10/2013 01:48 PM, Julien Grall wrote:
> >>
> >> 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 ? :)
> >
> >
> > Sorry for the lag ;-)
> >
> >
> >>
> >>> 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)
> >
> >
> > I'd say that is intended. I think those command lines directly under /chosen
> > should have the highest priority. If someone has
> > /chosen/xen,dom0-bootargs, that should be used instead of a most likely
> > hard-coded value under modules.
> 
> I don't  think people use bootargs in module.

They are documented as existing in
docs/misc/arm/device-tree/booting.txt, so something would need to change
in either the code or the docs I think.

I don't think I mind which options take precedence so long as it is
clearly documented what is what. Although there is something nice about
having the stuff under modules be a complete consistent set of address
+cmdline I guess.

Ian.


>  So we can get a rid of this code.
> Ian, what do you think?
> 
> Cheers,
> 



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