Re: [PATCH v2 20/25] x86: Fix x86_cpu_new() error API violations

[Igor Mammedov]

On Wed, 24 Jun 2020 10:37:32 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> The Error ** argument must be NULL, &error_abort, &error_fatal, or a
> pointer to a variable containing NULL.  Passing an argument of the
> latter kind twice without clearing it in between is wrong: if the
> first call sets an error, it no longer points to NULL for the second
> call.
> 
> x86_cpu_new() is wrong that way: it passes &local_err to
> object_property_set_uint() without checking it, and then to
> qdev_realize().  Harmless, because the former can't actually fail
> here.
> 
> Fix by checking for failure right away.  While there, replace
> qdev_realize(); object_unref() by qdev_realize_and_unref().
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  hw/i386/x86.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index 34229b45c7..3a7029e6db 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -118,16 +118,10 @@ uint32_t x86_cpu_apic_id_from_index(X86MachineState 
> *x86ms,
>  
>  void x86_cpu_new(X86MachineState *x86ms, int64_t apic_id, Error **errp)
>  {
> -    Object *cpu = NULL;
> -    Error *local_err = NULL;
> +    Object *cpu = object_new(MACHINE(x86ms)->cpu_type);
>  
> -    cpu = object_new(MACHINE(x86ms)->cpu_type);
> -
> -    object_property_set_uint(cpu, apic_id, "apic-id", &local_err);
> -    qdev_realize(DEVICE(cpu), NULL, &local_err);
> -
> -    object_unref(cpu);
> -    error_propagate(errp, local_err);
> +    object_property_set_uint(cpu, apic_id, "apic-id", &error_abort);
it may fail here if user specified wrong cpu flags, but there is nothing we can 
do to fix it.
perhaps error_fatal would suit this case better?
 

> +    qdev_realize_and_unref(DEVICE(cpu), NULL, errp);
>  }
>  
>  void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)