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

[David Hildenbrand]

On 25.08.23 08:57, ThinerLogoer wrote:

Hello,

At 2023-08-23 23:34:11, "David Hildenbrand" <da...@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 <logoerthin...@163.com>
Signed-off-by: David Hildenbrand <da...@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..dbcd124d45 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1382,7 +1382,9 @@ void machine_run_board_init(MachineState *machine, const 
char *mem_path, Error *
                                  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",
+                " Change the object's 'id' to something else or disable"
+                " automatic creation of the default RAM backend by setting"
+                " the 'memory-backend' machine property",
                 machine_class->default_ram_id);
             return;
         }

I'd suggest a more explicit version:

                 " Change the object's 'id' to something else or disable"
                 " automatic creation of the default RAM backend by appending"
                 "  'memory-backend={machine_class->default_ram_id}' in '-machine' 
arguments",

Thanks, I'll do:

diff --git a/hw/core/machine.c b/hw/core/machine.c
index f0d35c6401..cd0fd6cdd1 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1382,8 +1382,10 @@ void machine_run_board_init(MachineState *machine, const 
char *mem_path, Error *
                                  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",
-                machine_class->default_ram_id);
+                " Change the object's 'id' to something else or disable"
+                " automatic creation of the default RAM backend by appending"
+                " 'memory-backend=%s' in '-machine' arguments",
+                machine_class->default_ram_id, machine_class->default_ram_id);
             return;
         }
         if (!create_default_memdev(current_machine, mem_path, errp)) {


--
Cheers,

David / dhildenb