commit cb61bc8a42da1a971079767e63df4503b6ab2efb
Author: Anatol Pomozov <anatol.pomozov@gmail.com>
Date:   Mon Jan 29 10:08:53 2018 -0800

    multiboot: Make elf64 loading functionality compatible with GRUB
    
    GRUB is a reference multiboot implementation and supports loading elf64
    binaries. Make QEMU to work similar was as GRUB.

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 5bc0a2cddb..0907e42a39 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -193,11 +193,6 @@ int load_multiboot(FWCfgState *fw_cfg,
         int kernel_size;
         fclose(f);
 
-        if (((struct elf64_hdr*)header)->e_machine == EM_X86_64) {
-            error_report("Cannot load x86-64 image, give a 32bit one.");
-            exit(1);
-        }
-
         kernel_size = load_elf(kernel_filename, NULL, NULL, &elf_entry,
                                &elf_low, &elf_high, 0, I386_ELF_MACHINE,
                                0, 0);