diff --git a/src/mainboard/emulation/qemu-q35/bootblock.c b/src/mainboard/emulation/qemu-q35/bootblock.c
new file mode 100644
index 0000000..939a4e6
--- /dev/null
+++ b/src/mainboard/emulation/qemu-q35/bootblock.c
@@ -0,0 +1,33 @@
+#include <arch/io.h>
+
+/* Just define these here, there is no gm35.h file to include. */
+#define D0F0_PCIEXBAR_LO 0x60
+#define D0F0_PCIEXBAR_HI 0x64
+
+static void bootblock_northbridge_init(void)
+{
+	uint32_t reg;
+
+	/*
+	 * The "io" variant of the config access is explicitly used to
+	 * setup the PCIEXBAR because CONFIG_MMCONF_SUPPORT_DEFAULT is set to
+	 * to true. That way all subsequent non-explicit config accesses use
+	 * MCFG. This code also assumes that bootblock_northbridge_init() is
+	 * the first thing called in the non-asm boot block code. The final
+	 * assumption is that no assembly code is using the
+	 * CONFIG_MMCONF_SUPPORT_DEFAULT option to do PCI config acceses.
+	 *
+	 * The PCIEXBAR is assumed to live in the memory mapped IO space under
+	 * 4GiB.
+	 */
+	reg = 0;
+	pci_io_write_config32(PCI_DEV(0,0,0), D0F0_PCIEXBAR_HI, reg);
+	reg = CONFIG_MMCONF_BASE_ADDRESS | 1; /* 256MiB - 0-255 buses. */
+	pci_io_write_config32(PCI_DEV(0,0,0), D0F0_PCIEXBAR_LO, reg);
+}
+
+static void bootblock_mainboard_init(void)
+{
+	bootblock_northbridge_init();
+	bootblock_southbridge_init();
+}