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..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)) {
Hi Markus,
error_setg()'s function comment specifies:
* The resulting message should be a single phrase, with no newline or
* trailing punctuation.
Please use error_append_hint(), like so
Please see the patch description: "Unfortunately, we cannot use error_append_hint(),
because the caller passes &error_fatal."
How should I deal with that?
qapi/error.h tells you :)
* = Creating errors =
[...]
* Create an error and add additional explanation:
* error_setg(errp, "invalid quark");
* error_append_hint(errp, "Valid quarks are up, down, strange, "
* "charm, top, bottom.\n");
* This may require use of ERRP_GUARD(); more on that below.
[...]
* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
* - It must not be dereferenced, because it may be null.
* - It should not be passed to error_prepend() or
* error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.
*
* Using it when it's not needed is safe, but please avoid cluttering
* the source with useless code.
*
* = Converting to ERRP_GUARD() =
*
* To convert a function to use ERRP_GUARD():
*
* 0. If the Error ** parameter is not named @errp, rename it to
* @errp.
*
* 1. Add an ERRP_GUARD() invocation, by convention right at the
* beginning of the function. This makes @errp safe to use.
*
* 2. Replace &err by errp, and err by *errp. Delete local variable
* @err.
*
* 3. Delete error_propagate(errp, *errp), replace
* error_propagate_prepend(errp, *errp, ...) by error_prepend(errp, ...)
*
* 4. Ensure @errp is valid at return: when you destroy *errp, set
* *errp = NULL.
*
* Example:
*
* bool fn(..., Error **errp)
* {
* Error *err = NULL;
*
* foo(arg, &err);
* if (err) {
* handle the error...
* error_propagate(errp, err);
* return false;
* }
* ...
* }
*
* becomes
*
* bool fn(..., Error **errp)
* {
* ERRP_GUARD();
*
* foo(arg, errp);
* if (*errp) {
* handle the error...
* return false;
* }
* ...
* }
*
* For mass-conversion, use scripts/coccinelle/errp-guard.cocci.
Questions?