[PATCH] arm/efi: Handle Xen bootargs from both xen.cfg and DT

[Luca Fancellu <luca.fancellu@xxxxxxx>]

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, if xen,xen-bootargs is found in the
device tree, it is used for xen boot arguments regardless they
are specified in the Xen configuration file or not.

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
 docs/misc/efi.pandoc        | 4 ++++
 xen/arch/arm/efi/efi-boot.h | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
index abafb3452758..b7d99de87f15 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 a device tree value has a precedence over the configuration file.
 
 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 c4ed41284597..fc1f2b9ad60e 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -497,6 +497,13 @@ static void __init efi_arch_handle_cmdline(CHAR16 
*image_name,
     if ( chosen < 0 )
         blexit(L"Unable to find chosen node");
 
+    /* If xen,bootargs is found in /chosen, use it for Xen */
+    if ( fdt_get_property(fdt, chosen, "xen,xen-bootargs", NULL) )
+    {
+        PrintStr(L"Using Xen boot arguments from device tree.\r\n");
+        return;
+    }
+
     status = efi_bs->AllocatePool(EfiBootServicesData, EFI_PAGE_SIZE, (void 
**)&buf);
     if ( EFI_ERROR(status) )
         PrintErrMesg(L"Unable to allocate string buffer", status);
-- 
2.17.1