From: Jason Andryuk <jandryuk@gmail.com>
Date: Wed, 24 Jun 2020 14:25:13 +0000 (-0400)
Subject: serialio: Preserve Xen DebugOutputPort
X-Git-Tag: rel-1.14.0~7
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=dd6a7e99b1c32ca66048673442cc7152efd08d2d;p=seabios.git

serialio: Preserve Xen DebugOutputPort

xen_preinit() runs early and changes DebugOutputPort.  qemu_preinit() runs
soon after.  inb on DebugOutputPort doesn't work on Xen, so the check
will always fail and DebugOutputPort will be cleared to 0 disabling
output.

Quick exit the function when running on Xen to preserve the modified
DebugOutputPort.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
---

diff --git a/src/hw/serialio.c b/src/hw/serialio.c
index 3163344..fa663b9 100644
--- a/src/hw/serialio.c
+++ b/src/hw/serialio.c
@@ -106,6 +106,10 @@ u16 DebugOutputPort VARFSEG = 0x402;
 void
 qemu_debug_preinit(void)
 {
+    /* Xen doesn't support checking if debug output is active. */
+    if (runningOnXen())
+        return;
+
     /* Check if the QEMU debug output port is active */
     if (CONFIG_DEBUG_IO &&
         inb(GET_GLOBAL(DebugOutputPort)) != QEMU_DEBUGCON_READBACK)