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, 15 insertions, 1 deletions

diff --git a/src/mainboard/emulation/qemu-q35/romstage.c b/src/mainboard/emulation/qemu-q35/romstage.c
index 2b8d9351c0..3e0870ffec 100644
--- a/src/mainboard/emulation/qemu-q35/romstage.c
+++ b/src/mainboard/emulation/qemu-q35/romstage.c
@@ -24,6 +24,7 @@
 
 asmlinkage void car_stage_entry(void)
 {
+	struct postcar_frame pcf;
 	i82801ix_early_init();
 	console_init();
 
@@ -31,5 +32,18 @@ asmlinkage void car_stage_entry(void)
 
 	timestamp_add_now(TS_START_ROMSTAGE);
 
-	run_ramstage();
+	/**
+	 * The LZMA decoder needs about 4 KiB stack.
+	 * Leave 1 KiB stack for general postcar code.
+	 */
+	if (postcar_frame_init(&pcf, 5 * KiB))
+		die("Unable to initialize postcar frame.\n");
+
+	/**
+	 * Run postcar to tear down CAR and load relocatable ramstage.
+	 * There's no CAR on qemu, but for educational purposes and
+	 * testing the postcar stage is used on qemu, too.
+	 */
+
+	run_postcar_phase(&pcf);
 }