Re: [Qemu-devel] [PATCH 20/24] machine: drop MachineState::cpu_model

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Jan 17, 2018 at 04:43:32PM +0100, Igor Mammedov wrote:
> The last user of it was machine type 'none', which used field
> to create CPU id user requested it on CLI with -cpu option.
> 
> We could compare pointers of MachineState::cpu_type and
> MachineClass::default_cpu_type to check for the same condition,
> and drop cpu_model concept completly from machine/boards code
> So that no one would try to reuse obsolete field and only
> place to deal with cpu model would be vl.c and
> foo_cpu_class_by_name() callbacks.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> CC: Eduardo Habkost <ehabkost@redhat.com>
> CC: Marcel Apfelbaum <marcel@redhat.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  include/hw/boards.h    |  1 -
>  hw/core/null-machine.c | 10 +++++++---
>  vl.c                   |  8 +++++++-
>  3 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 156b16f..decd0ec 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -246,7 +246,6 @@ struct MachineState {
>      char *kernel_filename;
>      char *kernel_cmdline;
>      char *initrd_filename;
> -    const char *cpu_model;
>      const char *cpu_type;
>      AccelState *accelerator;
>      CPUArchIdList *possible_cpus;
> diff --git a/hw/core/null-machine.c b/hw/core/null-machine.c
> index 864832d..c2e466c 100644
> --- a/hw/core/null-machine.c
> +++ b/hw/core/null-machine.c
> @@ -23,10 +23,13 @@
>  static void machine_none_init(MachineState *mch)
>  {
>      CPUState *cpu = NULL;
> +    MachineClass *mc = MACHINE_GET_CLASS(mch);
>  
> -    /* Initialize CPU (if a model has been specified) */
> -    if (mch->cpu_model) {
> -        cpu = cpu_init(mch->cpu_model);
> +    /* Initialize CPU if cpu_type pointer is user provided
> +     * (i.e. != to pointer tot static default cpu type string)
> +     */
> +    if (mch->cpu_type != mc->default_cpu_type) {
> +        cpu = cpu_create(mch->cpu_type);

This is a big assumption about the code that sets mch->cpu_type.
A simple g_strdup(machine_class->default_cpu_type) would break
this silently (as it won't trigger the assert() below).


>          if (!cpu) {
>              error_report("Unable to initialize CPU");
>              exit(1);
> @@ -54,6 +57,7 @@ static void machine_none_machine_init(MachineClass *mc)
>      mc->init = machine_none_init;
>      mc->max_cpus = 1;
>      mc->default_ram_size = 0;
> +    mc->default_cpu_type = TARGET_DEFAULT_CPU_TYPE;

Why do you need this?  Isn't it simpler to just leave
default_cpu_type=NULL here?


>  }
>  
>  DEFINE_MACHINE("none", machine_none_machine_init)
> diff --git a/vl.c b/vl.c
> index 2586f25..8aa0131 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4609,7 +4609,6 @@ int main(int argc, char **argv, char **envp)
>      current_machine->maxram_size = maxram_size;
>      current_machine->ram_slots = ram_slots;
>      current_machine->boot_order = boot_order;
> -    current_machine->cpu_model = cpu_model;
>  
>      parse_numa_opts(current_machine);
>  
> @@ -4619,6 +4618,13 @@ int main(int argc, char **argv, char **envp)
>          if (cpu_model) {
>              current_machine->cpu_type =
>                  cpu_parse_cpu_model(machine_class->default_cpu_type, cpu_model);
> +
> +            /* machine 'none' depends on default cpu type pointer not being
> +             * equal to resolved type name pointer to fugure out if type was
> +             * user provided, make sure that if it becomes not true in future
> +             * it won't beark silently */
> +            g_assert(
> +                current_machine->cpu_type != machine_class->default_cpu_type);
>          }
>      }
>  
> -- 
> 2.7.4
> 

-- 
Eduardo