Re: [Qemu-devel] [PATCH] qdev-monitor: Avoid exiting when hot-plugging two devices with the same bootindex value

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

On Wed, 2013-09-11 at 21:26 +0300, Marcel Apfelbaum wrote:
> Qemu is expected to quit if the same boot index value is used by two devices.
> However, hot-plugging a device with a bootindex value already used should
> fail with a friendly message rather than quitting a running VM.
> 
> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> ---
>  qdev-monitor.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 410cdcb..654d086 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -24,6 +24,7 @@
>  #include "qmp-commands.h"
>  #include "sysemu/arch_init.h"
>  #include "qemu/config-file.h"
> +#include "sysemu/sysemu.h"
>  
>  /*
>   * Aliases were a bad idea from the start.  Let's keep them
> @@ -442,6 +443,31 @@ static BusState *qbus_find(const char *path)
>      }
>  }
>  
> +#define OBJ_PROP_BOOTINDEX "bootindex"
A drawback of this patch is that is based on the assumption that
all devices supporting boot ordering will have a property with the
same name: bootindex.
A more robust approach would be to have some kind of interface
for such devices with a single "getter" method: bootindex()

Any thoughts?
Thanks,
Marcel 

> +
> +static bool bootindex_colision(Object *obj, QemuOpts *opts)
> +{
> +    int32_t bootindex;
> +
> +    if (!object_property_find(obj, OBJ_PROP_BOOTINDEX, NULL)) {
> +        return false;
> +    }
> +
> +    /* avoid parsing by setting the property and then getting it typed */
> +    object_property_parse(obj, qemu_opt_get(opts, OBJ_PROP_BOOTINDEX),
> +                          OBJ_PROP_BOOTINDEX, NULL);
> +    bootindex = (int32_t)object_property_get_int(obj, OBJ_PROP_BOOTINDEX,
> +                                                 NULL);
> +
> +    if (bootindex >= 0) {
> +        if (get_boot_device(bootindex)) {
> +            return true;
> +        }
> +    }
> +
> +    return false;
> +}
> +
>  DeviceState *qdev_device_add(QemuOpts *opts)
>  {
>      ObjectClass *obj;
> @@ -502,6 +528,13 @@ DeviceState *qdev_device_add(QemuOpts *opts)
>      /* create device, set properties */
>      qdev = DEVICE(object_new(driver));
>  
> +    if (qdev_hotplug && bootindex_colision(OBJECT(qdev), opts)) {
> +        qerror_report(QERR_INVALID_PARAMETER_VALUE,
> +                      "bootindex", "an unused boot index value");
> +        qdev_free(qdev);
> +        return NULL;
> +    }
> +
>      if (bus) {
>          qdev_set_parent_bus(qdev, bus);
>      }