[PATCH v2 2/2] xen/common: add keyhandler to show Xen command line

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx> 

Currently there's no way to print Xen command line on the emergency
console for debugging purposes (e.g. 'xl' is not available in dom0).

Add new keyhander 'X' to do command line printout.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
v1: https://lore.kernel.org/xen-devel/20260730061459.2702672-2-dmukhin@xxxxxxxx/

Changes since v1:
- moved implementation into kernel.c
---
 xen/common/kernel.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index d1bef9ac2b2b..9f334c92e3ab 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -5,6 +5,7 @@
  */
 
 #include <xen/init.h>
+#include <xen/keyhandler.h>
 #include <xen/lib.h>
 #include <xen/errno.h>
 #include <xen/param.h>
@@ -505,6 +506,21 @@ static int __init cf_check param_init(void)
 __initcall(param_init);
 #endif
 
+static void cf_check show_hypervisor_info(unsigned char key)
+{
+    printk("'%c' pressed -> showing hypervisor information\n", key);
+    printk("Command line: %s\n", saved_cmdline);
+}
+
+static int __init cf_check misc_init(void)
+{
+    register_keyhandler('X', show_hypervisor_info,
+                        "show hypervisor information", 0);
+
+    return 0;
+}
+__initcall(misc_init);
+
 static long xenver_varbuf_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
     struct xen_varbuf user_str;
-- 
2.54.0