diff --git a/tools/firmware/hvmloader/Makefile b/tools/firmware/hvmloader/Makefile
index 84cba171cd6b..c7bc4006578a 100644
--- a/tools/firmware/hvmloader/Makefile
+++ b/tools/firmware/hvmloader/Makefile
@@ -25,7 +25,7 @@ ld-option = $(shell if $(LD) -v $(1) >/dev/null 2>&1; then echo y; else echo n;
 # SMBIOS spec requires format mm/dd/yyyy
 SMBIOS_REL_DATE ?= $(shell date +%m/%d/%Y)
 
-CFLAGS += $(CFLAGS_xeninclude) -fno-pic
+CFLAGS += $(CFLAGS_xeninclude) -fno-pic -mregparm=3
 
 # We mustn't use tools-only public interfaces.
 CFLAGS += -D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__
diff --git a/tools/firmware/hvmloader/smp.c b/tools/firmware/hvmloader/smp.c
index 5d46eee1c5f4..1b940cefd071 100644
--- a/tools/firmware/hvmloader/smp.c
+++ b/tools/firmware/hvmloader/smp.c
@@ -31,7 +31,7 @@
 
 static int ap_callin;
 
-static void __attribute__((regparm(1))) cpu_setup(unsigned int cpu)
+static void cpu_setup(unsigned int cpu)
 {
     printf(" - CPU%d ... ", cpu);
     cacheattr_init();