[xen stable-4.16] arm/efi: Handle Xen bootargs from both xen.cfg and DT

[patchbot@xxxxxxx]

commit cfd29b83a26f35f49f074f06169ce4cadfdebf0d
Author:     Luca Fancellu <luca.fancellu@xxxxxxx>
AuthorDate: Mon Dec 13 11:48:54 2021 +0000
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CommitDate: Thu Mar 10 09:41:53 2022 -0800

    arm/efi: Handle Xen bootargs from both xen.cfg and DT
    
    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@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    (cherry picked from commit f3999bc2e099c571e4583bff8f494b834b2f5f76)
---
 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 abafb34527..71fdc316b6 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 458cfbbed4..9f26798239 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -514,11 +514,26 @@ 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 )
     {
--
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