Re: [Qemu-devel] [PATCH 09/18] qdev: Add a pre-firmware init capability

[Andreas Färber]

Am 19.07.2012 20:53, schrieb address@hidden:
> From: Corey Minyard <address@hidden>
> 
> Some devices may need to do some firmware-type initialization before
> the firmware itself is initialized.  For instance, any device that
> adds SMBIOS table entries (like IPMI) will need to do that before
> the BIOS is initialized.
> 
> So add a list of devices that get initialized before the firmware
> initialization.  Since those devices get removed from the list so
> they don't get initialized twice, convert the qemu_opt_foreach() to
> use the safe list traversal.
> 
> Signed-off-by: Corey Minyard <address@hidden>

I'm not so thrilled by this interface...

This doesn't seem to have anything to do with the monitor, and
prefw_list doesn't really indicate it's a list of type names either, nor
does qdev_add_prefw_init() precisely indicate what it's doing.

Then, your implementation of qdev_prefw_init_check() is based on
re-iterating over -device options. That's not safe since there's other
ways to create a device - object_new() et al. and soon a qom_create QMP
command.

So what exactly is the problem you are trying to solve here? What needs
to happen before this step and until when does this need to happen? For
example, is this an ordering problem between device creation and
MemoryRegion setup in the machine?

My thinking is that if this is a generic problem unrelated to QOM
realize / DeviceState::init we could provide a new
DeviceState::init_firmware hook for that purpose and call it recursively
on all devices. If however this is just some PC quirk, we should not
model this at qdev level but locally in hw/pc.c, then you have more
degrees of freedom in designing some PC-internal API.

Regards,
Andreas

> ---
>  hw/pc.c           |    2 ++
>  hw/qdev-monitor.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/qdev.h         |    3 +++
>  qemu-option.c     |    4 ++--
>  4 files changed, 59 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/pc.c b/hw/pc.c
> index bedd5be..811d99c 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -1010,6 +1010,8 @@ void *pc_bios_init(const char *kernel_filename,
>      void *fw_cfg;
>      int linux_boot, i;
>  
> +    qdev_prefw_init_check();
> +
>      /* Initialize PC system firmware */
>      pc_system_firmware_init(rom_memory);
>  
> diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
> index 7915b45..bb8e955 100644
> --- a/hw/qdev-monitor.c
> +++ b/hw/qdev-monitor.c
> @@ -486,6 +486,58 @@ DeviceState *qdev_device_add(QemuOpts *opts)
>      return qdev;
>  }
>  
> +/*
> + * Some devices may need to be initialized before the firmware is
> + * initialized, so they may add information to the firmware
> + * structures.
> + */
> +typedef struct prefw_list {
> +    const char *name;
> +    struct prefw_list *next;
> +} prefw_list;
> +
> +prefw_list *prefw_init;
> +
> +void qdev_add_prefw_init(const char *name)
> +{
> +    prefw_list *e = g_malloc(sizeof(*e));
> +    e->name = name;
> +    e->next = prefw_init;
> +    prefw_init = e;
> +}
> +
> +static int prefw_check_func(QemuOpts *opts, void *opaque)
> +{
> +    DeviceState *dev;
> +    const char *driver;
> +    prefw_list *e;
> +
> +    driver = qemu_opt_get(opts, "driver");
> +    if (!driver) {
> +        return 0;
> +    }
> +
> +    for (e = prefw_init; e; e = e->next) {
> +        if (strcmp(driver, e->name) == 0) {
> +            dev = qdev_device_add(opts);
> +            if (!dev) {
> +                return -1;
> +            }
> +            qemu_opts_del(opts);
> +            break;
> +        }
> +    }
> +    return 0;
> +}
> +
> +void qdev_prefw_init_check(void)
> +{
> +    /* init generic devices */
> +    if (qemu_opts_foreach(qemu_find_opts("device"),
> +                          prefw_check_func, NULL, 1) != 0) {
> +        exit(1);
> +    }
> +}
>  
>  #define qdev_printf(fmt, ...) monitor_printf(mon, "%*s" fmt, indent, "", ## 
> __VA_ARGS__)
>  static void qbus_print(Monitor *mon, BusState *bus, int indent);
> diff --git a/hw/qdev.h b/hw/qdev.h
> index f4683dc..2be4c95 100644
> --- a/hw/qdev.h
> +++ b/hw/qdev.h
> @@ -167,6 +167,9 @@ int qdev_simple_unplug_cb(DeviceState *dev);
>  void qdev_machine_creation_done(void);
>  bool qdev_machine_modified(void);
>  
> +void qdev_add_prefw_init(const char *name);
> +void qdev_prefw_init_check(void);
> +
>  qemu_irq qdev_get_gpio_in(DeviceState *dev, int n);
>  void qdev_connect_gpio_out(DeviceState *dev, int n, qemu_irq pin);
>  
> diff --git a/qemu-option.c b/qemu-option.c
> index bb3886c..1d000f8 100644
> --- a/qemu-option.c
> +++ b/qemu-option.c
> @@ -709,10 +709,10 @@ int qemu_opt_set_bool(QemuOpts *opts, const char *name, 
> bool val)
>  int qemu_opt_foreach(QemuOpts *opts, qemu_opt_loopfunc func, void *opaque,
>                       int abort_on_failure)
>  {
> -    QemuOpt *opt;
> +    QemuOpt *opt, *next_opt;
>      int rc = 0;
>  
> -    QTAILQ_FOREACH(opt, &opts->head, next) {
> +    QTAILQ_FOREACH_SAFE(opt, &opts->head, next, next_opt) {
>          rc = func(opt->name, opt->str, opaque);
>          if (abort_on_failure  &&  rc != 0)
>              break;
> 


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