Re: [PATCH v2 5/7] target/i386/cpu: Improve errors for out of bounds property values

[Markus Armbruster <armbru@redhat.com>]

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

> On 10/10/24 12:01, Markus Armbruster wrote:
>> The error message for a "stepping" value that is out of bounds is a
>> bit odd:
>>      $ qemu-system-x86_64 -cpu qemu64,stepping=16
>>      qemu-system-x86_64: can't apply global qemu64-x86_64-cpu.stepping=16: Property .stepping doesn't take value 16 (minimum: 0, maximum: 15)
>> The "can't apply global" part is an unfortunate artifact of -cpu's
>> implementation.  Left for another day.
>> The remainder feels overly verbose.  Change it to
>>      qemu64-x86_64-cpu: can't apply global qemu64-x86_64-cpu.stepping=16: parameter 'stepping' can be at most 15
>> Likewise for "family", "model", and "tsc-frequency".
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>   target/i386/cpu.c | 20 +++++++++-----------
>>   1 file changed, 9 insertions(+), 11 deletions(-)
>
>
>> @@ -5623,16 +5622,15 @@ static void x86_cpuid_set_tsc_freq(Object *obj, Visitor *v, const char *name,
>>                                      void *opaque, Error **errp)
>>   {
>>       X86CPU *cpu = X86_CPU(obj);
>> -    const int64_t min = 0;
>>       const int64_t max = INT64_MAX;
>>       int64_t value;
>>         if (!visit_type_int(v, name, &value, errp)) {
>>           return;
>>       }
>> -    if (value < min || value > max) {
>> -        error_setg(errp, QERR_PROPERTY_VALUE_OUT_OF_RANGE, "",
>> -                   name ? name : "null", value, min, max);
>> +    if (value < 0 || value > max) {
>> +        error_setg(errp, "parameter '%s' can be at most %" PRId64,
>> +                   name ? name : "null", max);
>
> Confusing:
>
>     qemu64-x86_64-cpu: can't apply global qemu64-x86_64-cpu.stepping=-1: parameter 'stepping' can be at most 15

For better or worse, visit_type_uint64() with the string input visitor
parses -1 modulo 2^64, i.e. as 2^64-1, just like strtoul() & friends.

>>           return;
>>       }
>>