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

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

On 8/8/26 4:38 AM, dmukhin@ford.com wrote:
> On Fri, Aug 07, 2026 at 05:44:41PM -0700, Stefano Stabellini wrote:
>> On Mon, 3 Aug 2026, dmukhin@ford.com wrote:
>>> From: Denis Mukhin <dmukhin@ford.com>
>>>
>>> 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@ford.com>
>>> ---
>>> v1: https://lore.kernel.org/xen-devel/20260730061459.2702672-2-dmukhin@ford.com/
>>>
>>> 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);
>>
>> if CONFIG_CMDLINE_OVERRIDE is defined, saved_cmdline is empty. We could
>> at least do this:
>>
>> #ifdef CONFIG_CMDLINE_OVERRIDE
>>      printk("Bootloader command line ignored (CONFIG_CMDLINE_OVERRIDE=y)\n");
>> #else
>>      printk("Command line: %s\n", saved_cmdline);
>> #endif
> 
> Actually, CONFIG_CMDLINE can set the built-in command line which can be
> non-empty.
> 
> Perhaps, something like this:
> 
>      printk("Command line (built-in): %s\n", opt_builtin_cmdline);
> #ifndef CONFIG_CMDLINE_OVERRIDE
>      printk("Command line: %s\n", saved_cmdline);
> #endif
> 
> What do you think?

Considering that opt_builtin_cmdline is declared as __initconst won't it 
be an issue to print it in non-init function (show_hypervisor_info())? 
In other words, I expected that __init section should be freed at some 
point and I expect that it should be data abort here.

~ Oleksii