On Wed, 22 Sep 2021, Luca Fancellu wrote:
> Introduce the uefi,cfg-load DT property of /chosen
> node for ARM whose presence decide whether to force
> the load of the UEFI Xen configuration file.
>
> The logic is that if any multiboot,module is found in
> the DT, then the uefi,cfg-load property is used to see
> if the UEFI Xen configuration file is needed.
>
> Signed-off-by: Luca Fancellu <luca.fance...@arm.com>
The patch looks OK, just a couple of minor comments below.
> ---
> v2 changes:
> - Introduced uefi,cfg-load property
> - Add documentation about the property
> ---
> docs/misc/efi.pandoc | 2 ++
> xen/arch/arm/efi/efi-boot.h | 28 +++++++++++++++++++++++-----
> 2 files changed, 25 insertions(+), 5 deletions(-)
>
> diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
> index ac3cd58cae..e289c5e7ba 100644
> --- a/docs/misc/efi.pandoc
> +++ b/docs/misc/efi.pandoc
> @@ -14,6 +14,8 @@ loaded the modules and describes them in the device tree
> provided to Xen. If a
> bootloader provides a device tree containing modules then any configuration
> files are ignored, and the bootloader is responsible for populating all
> relevant device tree nodes.
> +The property "uefi,cfg-load" can be specified in the /chosen node to force
> Xen
> +to load the configuration file even if multiboot modules are found.
I think that, in addition to this, we also need to add the property to
docs/misc/arm/device-tree/booting.txt where our "official" device tree
bindings are maintained. I would add it below "Command lines" and before
"Creating Multiple Domains directly from Xen" maybe as a new chapter.
It could be called "Other Options" but other ideas could be valid too.
You can say that uefi,cfg-load is a boolean.
> Once built, `make install-xen` will place the resulting binary directly into
> the EFI boot partition, provided `EFI_VENDOR` is set in the environment (and
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index cf9c37153f..8ceeba4ad1 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -581,22 +581,40 @@ static void __init
> efi_arch_load_addr_check(EFI_LOADED_IMAGE *loaded_image)
>
> static bool __init efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
> {
> + bool skip_cfg_file = false;
> /*
> * For arm, we may get a device tree from GRUB (or other bootloader)
> * that contains modules that have already been loaded into memory. In
> - * this case, we do not use a configuration file, and rely on the
> - * bootloader to have loaded all required modules and appropriate
> - * options.
> + * this case, we search for the property uefi,cfg-load in the /chosen
> node
> + * to decide whether to skip the UEFI Xen configuration file or not.
> */
>
> fdt = lookup_fdt_config_table(SystemTable);
> dtbfile.ptr = fdt;
> dtbfile.need_to_free = false; /* Config table memory can't be freed. */
> - if ( !fdt || fdt_node_offset_by_compatible(fdt, 0, "multiboot,module") <
> 0 )
> +
> + if ( fdt_node_offset_by_compatible(fdt, 0, "multiboot,module") > 0 )
> + {
> + /* Locate chosen node */
> + int node = fdt_subnode_offset(fdt, 0, "chosen");
> + const void *cfg_load_prop;
> + int cfg_load_len;
> +
> + if ( node > 0 )
> + {
> + /* Check if uefi,cfg-load property exists */
> + cfg_load_prop = fdt_getprop(fdt, node, "uefi,cfg-load",
> + &cfg_load_len);
> + if ( !cfg_load_prop )
> + skip_cfg_file = true;
> + }
> + }
> +
> + if ( !fdt || !skip_cfg_file )
Just a suggestion, but rather than the double negative, wouldn't it be
simpler to define it as
bool load_cfg_file = true;
?
> {
> /*
> * We either have no FDT, or one without modules, so we must have a
> - * Xen EFI configuration file to specify modules. (dom0 required)
> + * Xen EFI configuration file to specify modules.
> */
Also mention in the commit message that you are taking the opportunity
to update this comment do remove "dom0 required".
> return true;
> }
> --
> 2.17.1
>
