Re: [Qemu-devel] [QEMU PATCH 2/3] per-machine-type CPU model alias system

["Andreas Färber" <afaerber@suse.de>]

Am 25.07.2012 20:18, schrieb Eduardo Habkost:
> This allow QEMUMachine structs to contain a list of CPU model aliases,
> used to keep command-line compatibility with older machine types, while
> making CPU model fixes available on newer machine types.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  hw/boards.h |    6 ++++++
>  vl.c        |   14 ++++++++++++++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/hw/boards.h b/hw/boards.h
> index f20f5ab..ad48399 100644
> --- a/hw/boards.h
> +++ b/hw/boards.h
> @@ -12,6 +12,11 @@ typedef void QEMUMachineInitFunc(ram_addr_t ram_size,
>                                   const char *initrd_filename,
>                                   const char *cpu_model);
>  
> +
> +typedef struct CPUModelAlias {
> +    const char *alias, *cpu_model;
> +} CPUModelAlias;
> +
>  typedef struct QEMUMachine {
>      const char *name;
>      const char *alias;
> @@ -27,6 +32,7 @@ typedef struct QEMUMachine {
>          no_sdcard:1;
>      int is_default;
>      const char *default_machine_opts;
> +    struct CPUModelAlias *cpu_aliases;
>      GlobalProperty *compat_props;
>      struct QEMUMachine *next;
>      const char *hw_version;
> diff --git a/vl.c b/vl.c
> index 34cc145..cd87e06 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1209,6 +1209,19 @@ QEMUMachine *find_default_machine(void)
>      return NULL;
>  }
>  
> +static const char *qemu_machine_resolve_cpu_model(QEMUMachine *m,
> +                                                  const char *cpu_model)
> +{
> +    if (cpu_model && m->cpu_aliases) {
> +        CPUModelAlias *a;
> +        for (a = m->cpu_aliases; a->alias; a++) {
> +            if (!strcmp(cpu_model, a->alias))
> +                return a->cpu_model;
> +        }
> +    }
> +    return cpu_model;
> +}
> +
>  void qemu_machine_init(QEMUMachine *machine,
>                         ram_addr_t ram_size,
>                         const char *boot_devices,
> @@ -1217,6 +1230,7 @@ void qemu_machine_init(QEMUMachine *machine,
>                         const char *initrd_filename,
>                         const char *cpu_model)
>  {
> +    cpu_model = qemu_machine_resolve_cpu_model(machine, cpu_model);
>      machine->init(ram_size, boot_devices,
>                    kernel_filename, kernel_cmdline, initrd_filename, cpu_model);
>  }
> 

If the model is specified with -M by user or libvirt, then all seems
fine, but renaming default CPUs like qemu64 et al. (as done for
non-default ones in the next patch) would break machines' cpu_init()
call. That's a fairly common use case for non-x86 machines.

The alternative would be to incept closer to object_new(), i.e. call an
alias resolution helper from the various cpu_*_init() functions.

Please keep me cc'ed.

Thanks,
Andreas

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