Re: [PATCH v3 7/7] hw/xen: Fix errp handling in xen_console

[David Woodhouse <dwmw2@infradead.org>]

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On Wed, 2025-01-15 at 17:49 +0100, Anthony PERARD wrote:
> 
> With those fixed: Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks. I've pushed those changes and am watching the pipeline at
https://gitlab.com/dwmw2/qemu/-/pipelines/1626804720

I'll probably send a pull request tomorrow. The patch now looks like
this:

From 8b44a3e39f36540818d99ef8cf79e64bba1ed9c3 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@amazon.co.uk>
Date: Wed, 15 Jan 2025 15:46:06 +0000
Subject: [PATCH] hw/xen: Fix errp handling in xen_console

When attempting to read the 'output' node, interpret any error *other*
than ENOENT as a fatal error. For ENOENT, fall back to serial_hd() to
find a character device, or create a null device.

Do not attempt to prepend to errp when serial_hd() fails; the error
isn't relevant (and prior to this change, wasn't set anyway).

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
---
 hw/char/xen_console.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index e61902461b..d03c188d1d 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -569,7 +569,7 @@ static void xen_console_device_create(XenBackendInstance *backend,
 
     snprintf(label, sizeof(label), "xencons%ld", number);
 
-    output = xs_node_read(xsh, XBT_NULL, NULL, NULL, "%s/%s", fe, "output");
+    output = xs_node_read(xsh, XBT_NULL, NULL, errp, "%s/%s", fe, "output");
     if (output) {
         /*
          * FIXME: sure we want to support implicit
@@ -581,19 +581,27 @@ static void xen_console_device_create(XenBackendInstance *backend,
                        output);
             goto fail;
         }
-    } else if (number) {
-        cd = serial_hd(number);
-        if (!cd) {
-            error_prepend(errp, "console: No serial device #%ld found: ",
-                          number);
-            goto fail;
-        }
+    } else if (errno != ENOENT) {
+        error_prepend(errp, "console: No valid chardev found: ");
+        goto fail;
     } else {
-        /* No 'output' node on primary console: use null. */
-        cd = qemu_chr_new(label, "null", NULL);
-        if (!cd) {
-            error_setg(errp, "console: failed to create null device");
-            goto fail;
+        error_free(*errp);
+        *errp = NULL;
+
+        if (number) {
+            cd = serial_hd(number);
+            if (!cd) {
+                error_setg(errp, "console: No serial device #%ld found",
+                           number);
+                goto fail;
+            }
+        } else {
+            /* No 'output' node on primary console: use null. */
+            cd = qemu_chr_new(label, "null", NULL);
+            if (!cd) {
+                error_setg(errp, "console: failed to create null device");
+                goto fail;
+            }
         }
     }
 
-- 
2.47.0



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