arch/x86: Fix payload loading via bounce-buffer

Fix regression (supposedly) after commit:

  23d62dd lib/bootmem: Add more bootmem tags

Without RELOCATABLE_RAMSTAGE, payload is allowed to overwrite
memory regions of the running ramstage. This case is handled
gracefully via a bounce-buffer implementation in arch/x86/boot.c.

Change-Id: I1c9bbdb963a7210d0817a7a990a70a1e4fc03624
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/26935
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/arch/x86/boot.c

@@ -203,7 +203,7 @@ static void jmp_payload(void *entry, unsigned long buffer, unsigned long size)
 
 int arch_supports_bounce_buffer(void)
 {
-	return 1;
+	return !IS_ENABLED(CONFIG_RELOCATABLE_RAMSTAGE);
 }
 
 int payload_arch_usable_ram_quirk(uint64_t start, uint64_t size)

src/lib/selfboot.c

@@ -350,6 +350,15 @@ static int payload_targets_usable_ram(struct segment *head)
 		if (payload_arch_usable_ram_quirk(ptr->s_dstaddr, ptr->s_memsz))
 			continue;
 
+		if (arch_supports_bounce_buffer() &&
+			bootmem_region_usable_with_bounce(ptr->s_dstaddr,
+						      ptr->s_memsz)) {
+			printk(BIOS_DEBUG,
+				"Payload is loaded over non-relocatable "
+				"ramstage. Will use bounce-buffer.\n");
+			return 1;
+		}
+
 		/* Payload segment not targeting RAM. */
 		printk(BIOS_ERR, "SELF Payload doesn't target RAM:\n");
 		printk(BIOS_ERR, "Failed Segment: 0x%lx, %lu bytes\n",