Re: [PATCH v3 11/11] machine: Improve error message when using default RAM backend id

[Philippe Mathieu-Daudé]

On 25/8/23 12:10, David Hildenbrand wrote:
> On 25.08.23 11:59, David Hildenbrand wrote:
> > On 25.08.23 11:56, Markus Armbruster wrote:
> > > David Hildenbrand <david@redhat.com> writes:
> > >
> > > > On 25.08.23 11:10, Markus Armbruster wrote:
> > > > > David Hildenbrand <david@redhat.com> writes:
> > > > >
> > > > > > On 25.08.23 08:57, ThinerLogoer wrote:
> > > > > > > Hello,
> > > > > > >
> > > > > > > At 2023-08-23 23:34:11, "David Hildenbrand" <david@redhat.com> 
> > > > > > > wrote:
> > > > > > > > For migration purposes, users might want to reuse the default RAM
> > > > > > > > backend id, but specify a different memory backend.
> > > > > > > >
> > > > > > > > For example, to reuse "pc.ram" on q35, one has to set
> > > > > > > >        -machine q35,memory-backend=pc.ram
> > > > > > > > Only then, can a memory backend with the id "pc.ram" be created
> > > > > > > > manually.
> > > > > > > >
> > > > > > > > Let's improve the error message.
> > > > > > > >
> > > > > > > > Unfortuantely, we cannot use error_append_hint(), because the 
> > > > > > > > caller
> > > > > > > > passes &error_fatal.
> > > > > > > >
> > > > > > > > Suggested-by: ThinerLogoer <logoerthiner1@163.com>
> > > > > > > > Signed-off-by: David Hildenbrand <david@redhat.com>
> > > > > > > > ---
> > > > > > > > hw/core/machine.c | 4 +++-
> > > > > > > > 1 file changed, 3 insertions(+), 1 deletion(-)


> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index f0d35c6401..09f40c7f07 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -1352,6 +1352,7 @@ out:
>
>   void machine_run_board_init(MachineState *machine, const char 
> *mem_path, Error **errp)
>   {
> +    ERRP_GUARD();
>       MachineClass *machine_class = MACHINE_GET_CLASS(machine);
>       ObjectClass *oc = object_class_by_name(machine->cpu_type);
>       CPUClass *cc;
> @@ -1380,9 +1381,13 @@ void machine_run_board_init(MachineState 
> *machine, const char *mem_path, Error *
>                  numa_uses_legacy_mem()) {
>           if (object_property_find(object_get_objects_root(),
>                                    machine_class->default_ram_id)) {
> -            error_setg(errp, "object name '%s' is reserved for the 
> default"
> -                " RAM backend, it can't be used for any other purposes."
> -                " Change the object's 'id' to something else",
> +            error_setg(errp, "object's id '%s' is reserved for the 
> default"
> +                " RAM backend, it can't be used for any other purposes",
> +                machine_class->default_ram_id);
> +            error_append_hint(errp,
> +                "Change the object's 'id' to something else or disable"
> +                " automatic creation of the default RAM backend by 
> setting"
> +                " 'memory-backend=%s' with '-machine'.\n",
>                   machine_class->default_ram_id);
>               return;
>           }

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>