[SeaBIOS] [PATCH v2] Preserve Xen DebugOutputPort

Jason Andryuk posted 1 patch 13 weeks ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/seabios tags/patchew/20200624142513.14270-1-jandryuk@gmail.com
src/hw/serialio.c | 4 ++++
1 file changed, 4 insertions(+)

[SeaBIOS] [PATCH v2] Preserve Xen DebugOutputPort

Posted by Jason Andryuk 13 weeks ago
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>

v2
Re-word comment
---
 src/hw/serialio.c | 4 ++++
 1 file changed, 4 insertions(+)

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)
-- 
2.25.1
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[SeaBIOS] Re: [PATCH v2] Preserve Xen DebugOutputPort

Posted by Kevin O'Connor 13 weeks ago
On Wed, Jun 24, 2020 at 10:25:13AM -0400, Jason Andryuk wrote:
> 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.

Thanks - I committed this change.

-Kevin
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[SeaBIOS] Re: [PATCH v2] Preserve Xen DebugOutputPort

Posted by Jason Andryuk 13 weeks ago
On Wed, Jun 24, 2020 at 11:46 AM Kevin O'Connor <kevin@koconnor.net> wrote:
>
> On Wed, Jun 24, 2020 at 10:25:13AM -0400, Jason Andryuk wrote:
> > 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.
>
> Thanks - I committed this change.

Thank you!

-Jason
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