Re: [Qemu-block] [Qemu-devel] [RFC PATCH 5/6] vl: Create block backends before setting machine properties

[Philippe Mathieu-Daudé]

On 2/25/19 7:37 PM, Markus Armbruster wrote:
> qemu-system-FOO's main() acts on command line arguments in its own
> idiosyncratic order.  There's not much method to its madness.
> Whenever we find a case where one kind of command line argument needs
> to refer to something created for another kind later, we rejigger the
> order.
> 
> Block devices get created long after machine properties get processed.
> Therefore, block device machine properties can be created, but not
> set.  No such properties exist.  But the next commit will create some.
> Time to rejigger again: create block devices earlier.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  vl.c | 66 ++++++++++++++++++++++++++++++------------------------------
>  1 file changed, 33 insertions(+), 33 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index 6ce3d2d448..5cb0810ffa 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4232,6 +4232,39 @@ int main(int argc, char **argv, char **envp)
>          exit(0);
>      }
>  

Can we extract this from the main, maybe as "parse_blockdev()"? This
will ease further rejigger :)

> +    /* If the currently selected machine wishes to override the units-per-bus
> +     * property of its default HBA interface type, do so now. */
> +    if (machine_class->units_per_default_bus) {
> +        override_max_devs(machine_class->block_default_type,
> +                          machine_class->units_per_default_bus);
> +    }
> +
> +    /* open the virtual block devices */
> +    while (!QSIMPLEQ_EMPTY(&bdo_queue)) {
> +        BlockdevOptions_queue *bdo = QSIMPLEQ_FIRST(&bdo_queue);
> +
> +        QSIMPLEQ_REMOVE_HEAD(&bdo_queue, entry);
> +        loc_push_restore(&bdo->loc);
> +        qmp_blockdev_add(bdo->bdo, &error_fatal);
> +        loc_pop(&bdo->loc);
> +        qapi_free_BlockdevOptions(bdo->bdo);
> +        g_free(bdo);
> +    }
> +    if (snapshot || replay_mode != REPLAY_MODE_NONE) {
> +        qemu_opts_foreach(qemu_find_opts("drive"), drive_enable_snapshot,
> +                          NULL, NULL);
> +    }
> +    if (qemu_opts_foreach(qemu_find_opts("drive"), drive_init_func,
> +                          &machine_class->block_default_type, &error_fatal)) 
> {
> +        /* We printed help */
> +        exit(0);
> +    }
> +
> +    default_drive(default_cdrom, snapshot, 
> machine_class->block_default_type, 2,
> +                  CDROM_OPTS);
> +    default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
> +    default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
> +

Can you add a comment here such:

   /*
    * Arguments setting properties on devices has to be processed before
    * the following qemu_opt_foreach(...machine_set_property...) call.
    */

>      machine_opts = qemu_get_machine_opts();
>      qemu_opt_foreach(machine_opts, machine_set_property, current_machine,
>                       &error_fatal);
> @@ -4355,39 +4388,6 @@ int main(int argc, char **argv, char **envp)
>      ram_mig_init();
>      dirty_bitmap_mig_init();
>  
> -    /* If the currently selected machine wishes to override the units-per-bus
> -     * property of its default HBA interface type, do so now. */
> -    if (machine_class->units_per_default_bus) {
> -        override_max_devs(machine_class->block_default_type,
> -                          machine_class->units_per_default_bus);
> -    }
> -
> -    /* open the virtual block devices */
> -    while (!QSIMPLEQ_EMPTY(&bdo_queue)) {
> -        BlockdevOptions_queue *bdo = QSIMPLEQ_FIRST(&bdo_queue);
> -
> -        QSIMPLEQ_REMOVE_HEAD(&bdo_queue, entry);
> -        loc_push_restore(&bdo->loc);
> -        qmp_blockdev_add(bdo->bdo, &error_fatal);
> -        loc_pop(&bdo->loc);
> -        qapi_free_BlockdevOptions(bdo->bdo);
> -        g_free(bdo);
> -    }
> -    if (snapshot || replay_mode != REPLAY_MODE_NONE) {
> -        qemu_opts_foreach(qemu_find_opts("drive"), drive_enable_snapshot,
> -                          NULL, NULL);
> -    }
> -    if (qemu_opts_foreach(qemu_find_opts("drive"), drive_init_func,
> -                          &machine_class->block_default_type, &error_fatal)) 
> {
> -        /* We printed help */
> -        exit(0);
> -    }
> -
> -    default_drive(default_cdrom, snapshot, 
> machine_class->block_default_type, 2,
> -                  CDROM_OPTS);
> -    default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
> -    default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
> -
>      qemu_opts_foreach(qemu_find_opts("mon"),
>                        mon_init_func, NULL, &error_fatal);
>  

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>