Currently the Xen UEFI stub can accept Xen boot arguments from
the Xen configuration file using the "options=" keyword, but also
directly from the device tree specifying xen,xen-bootargs
property.

When the configuration file is used, device tree boot arguments
are ignored and overwritten even if the keyword "options=" is
not used.

This patch handle this case, so if the Xen configuration file is not
specifying boot arguments, the device tree boot arguments will be
used, if they are present.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
---
v2 changes:
 - Changed logic, now xen cfg bootarg value has precedence over DT
---
 docs/misc/efi.pandoc        |  4 ++++
 xen/arch/arm/efi/efi-boot.h | 15 +++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
index abafb3452758..71fdc316b67b 100644
--- a/docs/misc/efi.pandoc
+++ b/docs/misc/efi.pandoc
@@ -249,6 +249,10 @@ UEFI stub for module loading.
 When adding DomU modules to device tree, also add the property
 xen,uefi-cfg-load under chosen for Xen to load the Xen config file.
 Otherwise, Xen will skip the config file and rely on device tree alone.
+When using the Xen configuration file in conjunction with the device tree, you
+can specify the Xen boot arguments in the configuration file with the "options="
+keyword or in the device tree with the "xen,xen-bootargs" property, but be
+aware that the Xen configuration file value has a precedence over the DT value.
 
 Example 1 of how to boot a true dom0less configuration:
 
diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index 4fb345f225c8..ae8627134e5a 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -503,11 +503,26 @@ static void __init efi_arch_handle_cmdline(CHAR16 *image_name,
 
     if ( cfgfile_options )
     {
+        PrintMessage(L"Using bootargs from Xen configuration file.");
         prop_len += snprintf(buf + prop_len,
                                EFI_PAGE_SIZE - prop_len, " %s", cfgfile_options);
         if ( prop_len >= EFI_PAGE_SIZE )
             blexit(L"FDT string overflow");
     }
+    else
+    {
+        /* Get xen,xen-bootargs in /chosen if it is specified */
+        const char *dt_bootargs_prop = fdt_getprop(fdt, chosen,
+                                                   "xen,xen-bootargs", NULL);
+        if ( dt_bootargs_prop )
+        {
+            PrintMessage(L"Using bootargs from device tree.");
+            prop_len += snprintf(buf + prop_len, EFI_PAGE_SIZE - prop_len,
+                                 " %s", dt_bootargs_prop);
+            if ( prop_len >= EFI_PAGE_SIZE )
+                blexit(L"FDT string overflow");
+        }
+    }
 
     if ( cmdline_options )
     {
-- 
2.17.1

On Mon, 13 Dec 2021, Luca Fancellu wrote:
> Currently the Xen UEFI stub can accept Xen boot arguments from
> the Xen configuration file using the "options=" keyword, but also
> directly from the device tree specifying xen,xen-bootargs
> property.
> 
> When the configuration file is used, device tree boot arguments
> are ignored and overwritten even if the keyword "options=" is
> not used.
> 
> This patch handle this case, so if the Xen configuration file is not
> specifying boot arguments, the device tree boot arguments will be
> used, if they are present.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
> v2 changes:
>  - Changed logic, now xen cfg bootarg value has precedence over DT
> ---
>  docs/misc/efi.pandoc        |  4 ++++
>  xen/arch/arm/efi/efi-boot.h | 15 +++++++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
> index abafb3452758..71fdc316b67b 100644
> --- a/docs/misc/efi.pandoc
> +++ b/docs/misc/efi.pandoc
> @@ -249,6 +249,10 @@ UEFI stub for module loading.
>  When adding DomU modules to device tree, also add the property
>  xen,uefi-cfg-load under chosen for Xen to load the Xen config file.
>  Otherwise, Xen will skip the config file and rely on device tree alone.
> +When using the Xen configuration file in conjunction with the device tree, you
> +can specify the Xen boot arguments in the configuration file with the "options="
> +keyword or in the device tree with the "xen,xen-bootargs" property, but be
> +aware that the Xen configuration file value has a precedence over the DT value.
>  
>  Example 1 of how to boot a true dom0less configuration:
>  
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index 4fb345f225c8..ae8627134e5a 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -503,11 +503,26 @@ static void __init efi_arch_handle_cmdline(CHAR16 *image_name,
>  
>      if ( cfgfile_options )
>      {
> +        PrintMessage(L"Using bootargs from Xen configuration file.");
>          prop_len += snprintf(buf + prop_len,
>                                 EFI_PAGE_SIZE - prop_len, " %s", cfgfile_options);
>          if ( prop_len >= EFI_PAGE_SIZE )
>              blexit(L"FDT string overflow");
>      }
> +    else
> +    {
> +        /* Get xen,xen-bootargs in /chosen if it is specified */
> +        const char *dt_bootargs_prop = fdt_getprop(fdt, chosen,
> +                                                   "xen,xen-bootargs", NULL);
> +        if ( dt_bootargs_prop )
> +        {
> +            PrintMessage(L"Using bootargs from device tree.");
> +            prop_len += snprintf(buf + prop_len, EFI_PAGE_SIZE - prop_len,
> +                                 " %s", dt_bootargs_prop);
> +            if ( prop_len >= EFI_PAGE_SIZE )
> +                blexit(L"FDT string overflow");
> +        }
> +    }
>  
>      if ( cmdline_options )
>      {
> -- 
> 2.17.1
>