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Re: [Qemu-devel] [PATCH 2/3] migration: Allow "device add" options to on


From: Ashijeet Acharya
Subject: Re: [Qemu-devel] [PATCH 2/3] migration: Allow "device add" options to only add migratable devices
Date: Thu, 15 Dec 2016 22:06:30 +0530

On Thu, Dec 15, 2016 at 9:49 PM, Dr. David Alan Gilbert
<address@hidden> wrote:
> * Ashijeet Acharya (address@hidden) wrote:
>> On Thu, Dec 15, 2016 at 9:35 PM, Dr. David Alan Gilbert
>> <address@hidden> wrote:
>> > * Ashijeet Acharya (address@hidden) wrote:
>> >> Introduce checks for the unmigratable flag in the VMStateDescription
>> >> structs of respective devices when user attempts to add them. If the
>> >> "--only-migratable" was specified, all unmigratable devices will
>> >> rightly fail to add. This feature is made compatible for both "-device"
>> >> and "-usbdevice" command line options and covers their hmp and qmp
>> >> counterparts as well.
>> >>
>> >> Signed-off-by: Ashijeet Acharya <address@hidden>
>> >> ---
>> >>  hw/usb/bus.c   | 15 +++++++++++++++
>> >>  qdev-monitor.c |  9 +++++++++
>> >>  2 files changed, 24 insertions(+)
>> >>
>> >> diff --git a/hw/usb/bus.c b/hw/usb/bus.c
>> >> index 25913ad..8796788 100644
>> >> --- a/hw/usb/bus.c
>> >> +++ b/hw/usb/bus.c
>> >> @@ -8,6 +8,7 @@
>> >>  #include "monitor/monitor.h"
>> >>  #include "trace.h"
>> >>  #include "qemu/cutils.h"
>> >> +#include "migration/migration.h"
>> >>
>> >>  static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int 
>> >> indent);
>> >>
>> >> @@ -686,6 +687,8 @@ USBDevice *usbdevice_create(const char *cmdline)
>> >>      const char *params;
>> >>      int len;
>> >>      USBDevice *dev;
>> >> +    ObjectClass *klass;
>> >> +    DeviceClass *dc;
>> >>
>> >>      params = strchr(cmdline,':');
>> >>      if (params) {
>> >> @@ -720,6 +723,18 @@ USBDevice *usbdevice_create(const char *cmdline)
>> >>          return NULL;
>> >>      }
>> >>
>> >> +    klass = object_class_by_name(f->name);
>> >
>> >> +    dc = DEVICE_CLASS(klass);
>> >
>> > Would qdev_get_device_class work here instead of that pair?
>>
>> No, because I believe that is defined as static in qdev_monitor.c
>> which was one of the reasons I faced a difficulty with this one.
>
> Hmm, I wonder if Markus can suggest a better way; qdev_get_device_class
> seems a lot more complex dealing iwth aliases and stuff, if we need that
> type of stuff.

Okay. I have grepped around for other uses of the macro DEVICE_CLASS
which is mostly during the initialization of the various devices and
we are not dealing with aliases probably because the device name is
rightly there. But similarly here, I am trusting the device name
stored in "f->name" more so after following the function call flow to
the lowest level and finding a similar call to object_class_by_name()
to get the ObjectClass of the device which passes the same name as
stored in f->name.

Ashijeet
>
> Dave
>
>> > (I was thinking you needed to check klass to make sure it wasn't null)
>>
>> Right. I will include the check in v2.
>>
>> Ashijeet
>> >
>> >> +    if (only_migratable) {
>> >> +        if (dc->vmsd->unmigratable) {
>> >> +            error_report("Device %s is not migratable, but 
>> >> --only-migratable "
>> >> +                         "was specified", f->name);
>> >> +            return NULL;
>> >> +        }
>> >> +    }
>> >> +
>> >>      if (f->usbdevice_init) {
>> >>          dev = f->usbdevice_init(bus, params);
>> >>      } else {
>> >> diff --git a/qdev-monitor.c b/qdev-monitor.c
>> >> index c73410c..81d01df 100644
>> >> --- a/qdev-monitor.c
>> >> +++ b/qdev-monitor.c
>> >> @@ -29,6 +29,7 @@
>> >>  #include "qemu/error-report.h"
>> >>  #include "qemu/help_option.h"
>> >>  #include "sysemu/block-backend.h"
>> >> +#include "migration/migration.h"
>> >>
>> >>  /*
>> >>   * Aliases were a bad idea from the start.  Let's keep them
>> >> @@ -577,6 +578,14 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error 
>> >> **errp)
>> >>          return NULL;
>> >>      }
>> >>
>> >> +    if (only_migratable) {
>> >> +        if (dc->vmsd->unmigratable) {
>> >> +            error_setg(errp, "Device %s is not migratable, but "
>> >> +                       "--only-migratable was specified", driver);
>> >> +            return NULL;
>> >> +        }
>> >> +    }
>> >> +
>> >>      /* find bus */
>> >>      path = qemu_opt_get(opts, "bus");
>> >>      if (path != NULL) {
>> >> --
>> >> 2.6.2
>> >>
>> > --
>> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK



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