diff --git a/xen/arch/x86/domain_builder/core.c b/xen/arch/x86/domain_builder/core.c
index 9335f3a9ebef..95cab06e6159 100644
--- a/xen/arch/x86/domain_builder/core.c
+++ b/xen/arch/x86/domain_builder/core.c
@@ -8,9 +8,37 @@
 #include <xen/lib.h>
 
 #include <asm/bootinfo.h>
+#include <asm/setup.h>
 
 #include "fdt.h"
 
+size_t __init builder_get_cmdline_size(struct boot_info *bi, int offset)
+{
+#ifdef CONFIG_DOMAIN_BUILDER
+    const void *fdt = bootstrap_map_bm(&bi->mods[HYPERLAUNCH_MODULE_IDX]);
+    int size = fdt_cmdline_prop_size(fdt, offset);
+
+    bootstrap_unmap();
+    return size < 0 ? 0 : (size_t) size;
+#else
+    return 0;
+#endif
+}
+
+int __init builder_get_cmdline(
+    struct boot_info *bi, int offset, char *cmdline, size_t size)
+{
+#ifdef CONFIG_DOMAIN_BUILDER
+    const void *fdt = bootstrap_map_bm(&bi->mods[HYPERLAUNCH_MODULE_IDX]);
+    int ret = fdt_cmdline_prop_copy(fdt, offset, cmdline, size);
+
+    bootstrap_unmap();
+    return ret;
+#else
+    return 0;
+#endif
+}
+
 void __init builder_init(struct boot_info *bi)
 {
     if ( IS_ENABLED(CONFIG_DOMAIN_BUILDER) )
diff --git a/xen/arch/x86/domain_builder/fdt.c b/xen/arch/x86/domain_builder/fdt.c
index 6bf1c4a297fe..f8ddb11b339e 100644
--- a/xen/arch/x86/domain_builder/fdt.c
+++ b/xen/arch/x86/domain_builder/fdt.c
@@ -57,6 +57,30 @@ static inline int __init fdt_get_prop_as_reg(
     return 0;
 }
 
+static int __init fdt_get_prop_as_offset(
+    const void *fdt, int node, const char *name, unsigned long *a)
+{
+    int ret, poffset;
+    const char *pname;
+    size_t nsize = strlen(name);
+
+    fdt_for_each_property_offset(poffset, fdt, node)
+    {
+        fdt_getprop_by_offset(fdt, poffset, &pname, &ret);
+
+        if ( ret < 0 || strlen(pname) != nsize )
+            continue;
+
+        if ( !strncmp(pname, name, nsize) )
+        {
+            *a = poffset;
+            return nsize;
+        }
+    }
+
+    return -ENOENT;
+}
+
 static int __init dom0less_module_node(
     void *fdt, int node, int size_size, int address_size)
 {
@@ -118,6 +142,16 @@ static int __init process_domain_node(
             printk("  kernel: boot module %d\n", idx);
             bi->mods[idx].type = BOOTMOD_KERNEL;
             bd->kernel = &bi->mods[idx];
+
+            /* If bootloader didn't set cmdline, see if FDT provides one. */
+            if ( bd->kernel->cmdline_pa &&
+                 !((char *)__va(bd->kernel->cmdline_pa))[0] )
+            {
+                int ret = fdt_get_prop_as_offset(
+                    fdt, node, "bootargs", &bd->kernel->cmdline_pa);
+                if ( ret > 0 )
+                    bd->kernel->fdt_cmdline = true;
+            }
         }
     }
 
diff --git a/xen/arch/x86/domain_builder/fdt.h b/xen/arch/x86/domain_builder/fdt.h
index 558d00a994fa..ab2b43872e25 100644
--- a/xen/arch/x86/domain_builder/fdt.h
+++ b/xen/arch/x86/domain_builder/fdt.h
@@ -27,6 +27,30 @@ static inline int __init fdt_cell_as_u64(const fdt32_t *cell, uint64_t *val)
     return 0;
 }
 
+static inline int __init fdt_cmdline_prop_size(const void *fdt, int offset)
+{
+    int ret;
+
+    fdt_get_property_by_offset(fdt, offset, &ret);
+
+    return ret;
+}
+
+static inline int __init fdt_cmdline_prop_copy(
+    const void *fdt, int offset, char *cmdline, size_t size)
+{
+    int ret;
+    const struct fdt_property *prop =
+        fdt_get_property_by_offset(fdt, offset, &ret);
+
+    if ( ret < 0 )
+        return ret;
+
+    ASSERT(size > ret);
+
+    return strlcpy(cmdline, prop->data, ret);
+}
+
 int has_hyperlaunch_fdt(struct boot_info *bi);
 int walk_hyperlaunch_fdt(struct boot_info *bi);
 #else
diff --git a/xen/arch/x86/include/asm/bootinfo.h b/xen/arch/x86/include/asm/bootinfo.h
index 683ca9dbe2e0..433a0e66121b 100644
--- a/xen/arch/x86/include/asm/bootinfo.h
+++ b/xen/arch/x86/include/asm/bootinfo.h
@@ -35,11 +35,13 @@ struct boot_module {
 
     /*
      * Module State Flags:
-     *   relocated: indicates module has been relocated in memory.
-     *   released:  indicates module's pages have been freed.
+     *   relocated:   indicates module has been relocated in memory.
+     *   released:    indicates module's pages have been freed.
+     *   fdt_cmdline: indicates module's cmdline is in the FDT.
      */
     bool relocated:1;
     bool released:1;
+    bool fdt_cmdline:1;
 
     /*
      * A boot module may need decompressing by Xen.  Headroom is an estimate of
diff --git a/xen/arch/x86/include/asm/domainbuilder.h b/xen/arch/x86/include/asm/domainbuilder.h
index aedc2b49f7c9..21221d8df8ec 100644
--- a/xen/arch/x86/include/asm/domainbuilder.h
+++ b/xen/arch/x86/include/asm/domainbuilder.h
@@ -3,6 +3,10 @@
 
 #include <asm/bootinfo.h>
 
+size_t __init builder_get_cmdline_size(struct boot_info *bi, int offset);
+int __init builder_get_cmdline(
+    struct boot_info *bi, int offset, char *cmdline, size_t size);
+
 void builder_init(struct boot_info *bi);
 
 #endif
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index d6e9d4c1769c..fda4fc71e205 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -971,7 +971,10 @@ static size_t __init domain_cmdline_size(
 {
     size_t s = bi->kextra ? strlen(bi->kextra) : 0;
 
-    s += bd->kernel->cmdline_pa ? strlen(__va(bd->kernel->cmdline_pa)) : 0;
+    if ( bd->kernel->fdt_cmdline )
+        s += builder_get_cmdline_size(bi, bd->kernel->cmdline_pa);
+    else
+        s += strlen(__va(bd->kernel->cmdline_pa));
 
     if ( s == 0 )
         return s;
@@ -1040,7 +1043,10 @@ static struct domain *__init create_dom0(struct boot_info *bi)
         if ( !(cmdline = xzalloc_array(char, cmdline_size)) )
             panic("Error allocating cmdline buffer for %pd\n", d);
 
-        if ( bd->kernel->cmdline_pa )
+        if ( bd->kernel->fdt_cmdline )
+            builder_get_cmdline(
+                bi, bd->kernel->cmdline_pa, cmdline, cmdline_size);
+        else
             strlcpy(cmdline,
                     cmdline_cook(__va(bd->kernel->cmdline_pa),bi->loader),
                     cmdline_size);
