mb/qemu-{i440fx,q35}: Use POSTCAR stage to load the ramstage

Qemu does not have a real CAR but postcar stage is still useful
for testing the stage.

The postcar stage is also mandatory for x86_64 to setup
pagetables for x86_64 ramstage.

Do not set up MTRRs, as qemu ignores them anyways.

Tested on qemu-i440fx and qemu-q35.

Change-Id: I6638534d99fde312e55b6a6be8c95e4cb25cca80
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/30499
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/mainboard/emulation/qemu-i440fx/exit_car.S b/src/mainboard/emulation/qemu-i440fx/exit_car.S
new file mode 100644
index 0000000000..06f1256768
--- /dev/null
+++ b/src/mainboard/emulation/qemu-i440fx/exit_car.S
@@ -0,0 +1,18 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2 of
+ * the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+.text
+.global chipset_teardown_car
+chipset_teardown_car:
+	/* There's no CAR to tear down */
+	ret