Re: [Qemu-devel] [PATCH v2 06/12] boards.h: Ignore migration for SMBus devices on older machines

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Corey Minyard (minyard@acm.org) wrote:
> On 11/27/18 10:01 AM, Dr. David Alan Gilbert wrote:
> > * Corey Minyard (minyard@acm.org) wrote:
> > > On 11/26/18 11:23 AM, Dr. David Alan Gilbert wrote:
> > > > * minyard@acm.org (minyard@acm.org) wrote:
> > > > > From: Corey Minyard <cminyard@mvista.com>
> > > > > 
> > > > > Migration capability is being added for pm_smbus and SMBus devices.
> > > > > This change will allow backwards compatibility to be kept when
> > > > > migrating back to an old qemu version.  Add a bool to the machine
> > > > > class tho keep smbus migration from happening.  Future changes
> > > > > will use this.
> > > > So this is also going to have to be in the 3.0 and 3.1 machine options
> > > > and maybe some other architectures?
> > > I'm not sure why it would need to be in both the 3.0 and 3.1 machine
> > > options.
> > > If this goes in, I'm assuming it's for 3.1 and it should only need to be
> > > there.
> > > That's if it's too late for 3.0.
> > You're out by 1-2 releases;  3.0 shipped in August, 3.1 is in freeze at
> > the moment (hence you've missed it unless some part of this is
> > critical); so this will go in during the 4.0 release.
> 
> Yes, you are right, this is for 4.0.
> 
> 
> > 
> > > The pm_smbus device is also used by mips fulong.  From what I can tell, that
> > > machine doesn't have any concept of backwards compatibility, so it seemed
> > > save to no worry about it there.  If it weren't for that, this bool could go
> > > into the
> > Yeh that's fine.
> > 
> > What about the eeprom's are they used more widely?
> 
> The only other I2C EEPROM I see is hw/nvram/eeprom_at24c.c.  That device is
> only
> configured for PPC.  It has a block device backend, too.  This is a little
> annoying
> because smbus_eeprom.c emulates an at24c02.  It would be nice to only have
> one of these.

Added in David and Laurent for odd-ppc stuff;  if I'm reading it right
it's not used by one of the versioned machines.

> I can add it to that file, too, it wouldn't be hard to do and I could put it
> into the
> x86 config to test.  It would be nicer to combine the two; smbus_eeprom
> seems
> like a hack to me.  at24c.c is done as an SMBus slave, its done as a raw I2C
> device, which is IMHO is more correct since the at24cxx devices are not
> SMBus
> devices, they are I2C devices.
> 
> In fact, smbus_eeprom.c is the only thing currently using the smbus_slave
> code.
> The IPMI interface on SMBus that I have pending uses the smbus_slave code,
> too,
> so perhaps there's value, though it's no big deal either way.  It would be
> nice to get
> this right the first time and not hack it up in the future.

Dave
> 
> Thanks,
> 
> -corey
> 
> 
> > 
> > Dave
> > 
> > > PC specific structure.
> > > 
> > > Thanks,
> > > 
> > > -corey
> > > 
> > > > Dave
> > > > 
> > > > > Signed-off-by: Corey Minyard <cminyard@mvista.com>
> > > > > Cc: Eduardo Habkost <ehabkost@redhat.com>
> > > > > Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> > > > > ---
> > > > >    hw/i386/pc_piix.c   | 1 +
> > > > >    hw/i386/pc_q35.c    | 1 +
> > > > >    include/hw/boards.h | 1 +
> > > > >    3 files changed, 3 insertions(+)
> > > > > 
> > > > > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> > > > > index cb28227cc3..3d1ccb1af1 100644
> > > > > --- a/hw/i386/pc_piix.c
> > > > > +++ b/hw/i386/pc_piix.c
> > > > > @@ -443,6 +443,7 @@ static void pc_i440fx_2_12_machine_options(MachineClass *m)
> > > > >        pc_i440fx_3_0_machine_options(m);
> > > > >        m->is_default = 0;
> > > > >        m->alias = NULL;
> > > > > +    m->smbus_no_migration_support = true;
> > > > >        SET_MACHINE_COMPAT(m, PC_COMPAT_2_12);
> > > > >    }
> > > > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > > > > index 90e88c9b28..0c6fca6a40 100644
> > > > > --- a/hw/i386/pc_q35.c
> > > > > +++ b/hw/i386/pc_q35.c
> > > > > @@ -324,6 +324,7 @@ static void pc_q35_2_12_machine_options(MachineClass *m)
> > > > >    {
> > > > >        pc_q35_3_0_machine_options(m);
> > > > >        m->alias = NULL;
> > > > > +    m->smbus_no_migration_support = true;
> > > > >        SET_MACHINE_COMPAT(m, PC_COMPAT_2_12);
> > > > >    }
> > > > > diff --git a/include/hw/boards.h b/include/hw/boards.h
> > > > > index f82f28468b..65314fbe2a 100644
> > > > > --- a/include/hw/boards.h
> > > > > +++ b/include/hw/boards.h
> > > > > @@ -207,6 +207,7 @@ struct MachineClass {
> > > > >        void (*numa_auto_assign_ram)(MachineClass *mc, NodeInfo *nodes,
> > > > >                                     int nb_nodes, ram_addr_t size);
> > > > >        bool ignore_boot_device_suffixes;
> > > > > +    bool smbus_no_migration_support;
> > > > >        HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
> > > > >                                               DeviceState *dev);
> > > > > -- 
> > > > > 2.17.1
> > > > > 
> > > > --
> > > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> > > 
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK