Re: [Qemu-devel] [PATCH v5 7/7] pc: add PC_I440FX_COMPAT to disable aercap for vifo device

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 2015-03-18 at 14:23 +0100, Michael S. Tsirkin wrote:
> typo in subject: vfio, not vifo.
> 
> On Thu, Mar 12, 2015 at 06:23:59PM +0800, Chen Fan wrote:
> > for piix4 chipset, we don't need to expose aer, so introduce
> > PC_I440FX_COMPAT for all piix4 machines to disable aercap,
> > and add HW_COMPAT_2_2 to disable aercap for all lower
> > than 2.3.
> > 
> > Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> 
> Well vfio is never migrated ATM.
> So why is compat code needed at all?

It's not for migration, it's to maintain current behavior on existing
platforms.  If someone gets an uncorrected AER error on q35 machine type
today, the VM stops.  With this change, AER would be exposed to the
guest and the guest could handle it.  The compat change therefore
maintains the stop VM behavior on existing q35 machine types.  As I
commented here, the 440fx part of this patch is unnecessary since AER
cannot be exposed to the guest on a conventional PCI chipset.  Thanks,

Alex

> > ---
> >  hw/i386/pc_piix.c   |  9 +++++++++
> >  hw/i386/pc_q35.c    |  4 ++++
> >  include/hw/compat.h | 10 ++++++++++
> >  3 files changed, 23 insertions(+)
> > 
> > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> > index 8eab4ba..ff9d312 100644
> > --- a/hw/i386/pc_piix.c
> > +++ b/hw/i386/pc_piix.c
> > @@ -307,6 +307,11 @@ static void pc_init1(MachineState *machine,
> >  
> >  static void pc_init_pci(MachineState *machine)
> >  {
> > +    static GlobalProperty pc_compat_props[] = {
> > +        PC_I440FX_COMPAT,
> > +        { /* end of list */ }
> > +    };
> > +    qdev_prop_register_global_list(pc_compat_props);
> >      pc_init1(machine, 1, 1);
> >  }
> >  
> > @@ -534,6 +539,10 @@ static QEMUMachine pc_i440fx_machine_v2_2 = {
> >      PC_I440FX_2_2_MACHINE_OPTIONS,
> >      .name = "pc-i440fx-2.2",
> >      .init = pc_init_pci_2_2,
> > +    .compat_props = (GlobalProperty[]) {
> > +        HW_COMPAT_2_2,
> > +        { /* end of list */ }
> > +    },
> >  };
> >  
> >  #define PC_I440FX_2_1_MACHINE_OPTIONS                           \
> > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > index c0f21fe..97afb7d 100644
> > --- a/hw/i386/pc_q35.c
> > +++ b/hw/i386/pc_q35.c
> > @@ -431,6 +431,10 @@ static QEMUMachine pc_q35_machine_v2_2 = {
> >      PC_Q35_2_2_MACHINE_OPTIONS,
> >      .name = "pc-q35-2.2",
> >      .init = pc_q35_init_2_2,
> > +    .compat_props = (GlobalProperty[]) {
> > +        HW_COMPAT_2_2,
> > +        { /* end of list */ }
> > +    },
> >  };
> >  
> >  #define PC_Q35_2_1_MACHINE_OPTIONS                      \
> > diff --git a/include/hw/compat.h b/include/hw/compat.h
> > index 313682a..40c974a 100644
> > --- a/include/hw/compat.h
> > +++ b/include/hw/compat.h
> > @@ -1,7 +1,17 @@
> >  #ifndef HW_COMPAT_H
> >  #define HW_COMPAT_H
> >  
> > +#define HW_COMPAT_2_2 PC_I440FX_COMPAT
> > +
> > +#define PC_I440FX_COMPAT \
> > +        {\
> > +            .driver   = "vfio-pci",\
> > +            .property = "x-aer",\
> > +            .value    = "off",\
> > +        }
> > +
> >  #define HW_COMPAT_2_1 \
> > +        HW_COMPAT_2_2, \
> >          {\
> >              .driver   = "intel-hda",\
> >              .property = "old_msi_addr",\
> > -- 
> > 1.9.3
> >