Cannot boot from disk with Heads in QEMU

I tried to run qemu with heads as the kernel and ramdisk, using the following commands in the linuxboot build directory:
sudo make BOARD=qemu KERNEL=../heads/build/qemu-linuxboot/bzImage INITRD=../heads/build/qemu-linuxboot/initrd.cpio.xz config
sudo make
sudo make run

The resulting run gave the following error while booting:
0.927991] Trying to unpack rootfs image as initramfs...

[ 3.745463] ------------[ cut here ]------------

[ 3.745973] WARNING: CPU: 0 PID: 1 at free_init_pages+0x2d/0x7a

[ 3.746226] Modules linked in:

[ 3.746551] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.62-heads #0

[ 3.746828] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015

[ 3.747190] task: ffff880006058000 task.stack: ffffc90000014000

[ 3.747443] RIP: 0010:free_init_pages+0x2d/0x7a

[ 3.747658] RSP: 0018:ffffc90000017e70 EFLAGS: 00000287

[ 3.747882] RAX: ffff880004da3000 RBX: ffff880000000000 RCX: ffff8800050f2818

[ 3.748152] RDX: ffff8800050f3000 RSI: ffff880004da2018 RDI: ffffffff81af162d

[ 3.748252] RBP: ffff8800050f3000 R08: 0000000000022080 R09: ffff880005ee81c0

[ 3.748252] R10: 0000000000000090 R11: ffff880005eece00 R12: 0000000080000000

[ 3.748252] R13: ffffffff81af162d R14: 0000000000000000 R15: 0000000000000000

[ 3.748252] FS: 0000000000000000(0000) GS:ffff880006400000(0000) knlGS:0000000000000000

[ 3.748252] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

[ 3.748252] CR2: 0000000000000000 CR3: 0000000002c0a000 CR4: 00000000000006f0

[ 3.748252] Call Trace:

[ 3.748252] ? do_early_param+0x89/0x89

[ 3.748252] free_initrd+0x73/0x8b

[ 3.748252] populate_rootfs+0xee/0xfc

[ 3.748252] ? clean_rootfs+0x12b/0x12b

[ 3.748252] do_one_initcall+0x92/0x138

[ 3.748252] ? do_early_param+0x89/0x89

[ 3.748252] kernel_init_freeable+0x146/0x1c6

[ 3.748252] ? rest_init+0x95/0x95

[ 3.748252] kernel_init+0x5/0xe6

[ 3.748252] ret_from_fork+0x35/0x40

[ 3.748252] Code: 86 ff 0f 00 00 41 55 49 89 fd 48 25 00 f0 ff ff 41 54 55 48 89 d5 48 81 e2 00 f0 ff ff 53 48 39 c6 75 08 48 89 f3 48 39 d5 74 08 <0f> 0b 48 89 d5 48 89 c3 48 39 eb 73 39 49 89 ec 48 89 df 49 29

[ 3.748252] ---[ end trace 1b64cae965fb82bb ]---

[ 3.767684] Freeing initrd memory: 3392K

It subsequently seemed to try a network boot - I expected an initrd shell.

Any idea what may be the problem?

Reproduce the failure from the linuxboot build directory with the documented BOARD=qemu, KERNEL, and INITRD commands, then start by examining the boot log around initramfs unpacking and free_initrd. Confirm why the expected initrd shell is not reached and document or implement the change needed for disk boot to continue correctly.