Re: [Qemu-devel] [PATCH] virtio-pci: fix missing device properties

[Eduardo Habkost]

On Wed, Jun 26, 2019 at 11:48:20AM +0200, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jun 26, 2019 at 3:56 AM Eduardo Habkost <address@hidden> wrote:
> >
> > On Wed, Jun 26, 2019 at 01:23:33AM +0200, Marc-André Lureau wrote:
> > > Since commit a4ee4c8baa37154 ("virtio: Helper for registering virtio
> > > device types"), virtio-gpu-pci, virtio-vga, and virtio-crypto-pci lost
> > > some properties: "ioeventfd" and "vectors". This may cause various
> > > issues, such as failing migration or invalid properties.
> > >
> > > Since those VirtioPCI devices do not have a base name, their class are
> > > initialized with virtio_pci_generic_base_class_init(). However, if the
> > > VirtioPCIDeviceTypeInfo provided a class_init which sets dc->props,
> > > the properties were overwritten by virtio_pci_generic_class_init().
> > >
> > > Instead, introduce an intermediary base-type to register the generic
> > > properties.
> > >
> > > Fixes: a4ee4c8baa37154f42b4dc6a13fee79268d15238
> > > Cc: address@hidden
> > > Signed-off-by: Marc-André Lureau <address@hidden>
> > > ---
> > >  hw/virtio/virtio-pci.c | 28 ++++++++++++++--------------
> > >  1 file changed, 14 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > > index e6d5467e54..62c4977332 100644
> > > --- a/hw/virtio/virtio-pci.c
> > > +++ b/hw/virtio/virtio-pci.c
> > > @@ -1913,13 +1913,6 @@ static void 
> > > virtio_pci_generic_class_init(ObjectClass *klass, void *data)
> > >      dc->props = virtio_pci_generic_properties;
> > >  }
> > >
> > > -/* Used when the generic type and the base type is the same */
> > > -static void virtio_pci_generic_base_class_init(ObjectClass *klass, void 
> > > *data)
> > > -{
> > > -    virtio_pci_base_class_init(klass, data);
> > > -    virtio_pci_generic_class_init(klass, NULL);
> > > -}
> > > -
> > >  static void virtio_pci_transitional_instance_init(Object *obj)
> > >  {
> > >      VirtIOPCIProxy *proxy = VIRTIO_PCI(obj);
> > > @@ -1938,14 +1931,13 @@ static void 
> > > virtio_pci_non_transitional_instance_init(Object *obj)
> > >
> > >  void virtio_pci_types_register(const VirtioPCIDeviceTypeInfo *t)
> > >  {
> > > +    char *base_name = NULL;
> > >      TypeInfo base_type_info = {
> > >          .name          = t->base_name,
> > >          .parent        = t->parent ? t->parent : TYPE_VIRTIO_PCI,
> > >          .instance_size = t->instance_size,
> > >          .instance_init = t->instance_init,
> > >          .class_size    = t->class_size,
> > > -        .class_init    = virtio_pci_base_class_init,
> > > -        .class_data    = (void *)t,
> > >          .abstract      = true,
> > >      };
> > >      TypeInfo generic_type_info = {
> > > @@ -1961,13 +1953,20 @@ void virtio_pci_types_register(const 
> > > VirtioPCIDeviceTypeInfo *t)
> > >
> > >      if (!base_type_info.name) {
> > >          /* No base type -> register a single generic device type */
> > > -        base_type_info.name = t->generic_name;
> > > -        base_type_info.class_init = virtio_pci_generic_base_class_init;
> > > -        base_type_info.interfaces = generic_type_info.interfaces;
> > > -        base_type_info.abstract = false;
> > > -        generic_type_info.name = NULL;
> > > +        /* use intermediate %s-base-type to add generic device props */
> > > +        base_name = g_strdup_printf("%s-base-type", t->generic_name);
> > > +        base_type_info.name = base_name;
> > > +        base_type_info.class_init = virtio_pci_generic_class_init;
> > > +
> > > +        generic_type_info.parent = base_name;
> > > +        generic_type_info.class_init = virtio_pci_base_class_init;
> > > +        generic_type_info.class_data = (void *)t;
> >
> > Why are you using virtio_pci_generic_class_init for the base
> > class, and virtio_pci_base_class_init for the subclass, but doing
> > exactly the opposite when t->base_name is set?
> >
> > Isn't it simpler to just initialize base_type_info.name and leave
> > all the rest alone?  Patch below.
> 
> That was my initial approach. But then I tested the backport on v4.0.0, you 
> get:
> 
> hw/display/virtio-vga.c:200:virtio_vga_class_init: Object
> 0x56247edbc0e0 is not an instance of type virtio-vga
> 
> The problem is that the introduced base class calls the t->class_init,
> which expects the final class (virtio-vga, not virtio-vga-base-type).

Ouch.  In this case:

Reviewed-by: Eduardo Habkost <address@hidden>

This would be much easier if we could append properties to
dc->props.  But this would be too complex for a
4.0-stable bug fix.

> 
> This seems to be limited to virtio-vga, and gone in upstream since the
> registration changed. But I would rather have the same patch
> reviewed/applied.
> 
> 
> >
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index e6d5467e54..3ee50a0783 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1913,13 +1913,6 @@ static void 
> > virtio_pci_generic_class_init(ObjectClass *klass, void *data)
> >      dc->props = virtio_pci_generic_properties;
> >  }
> >
> > -/* Used when the generic type and the base type is the same */
> > -static void virtio_pci_generic_base_class_init(ObjectClass *klass, void 
> > *data)
> > -{
> > -    virtio_pci_base_class_init(klass, data);
> > -    virtio_pci_generic_class_init(klass, NULL);
> > -}
> > -
> >  static void virtio_pci_transitional_instance_init(Object *obj)
> >  {
> >      VirtIOPCIProxy *proxy = VIRTIO_PCI(obj);
> > @@ -1938,8 +1931,11 @@ static void 
> > virtio_pci_non_transitional_instance_init(Object *obj)
> >
> >  void virtio_pci_types_register(const VirtioPCIDeviceTypeInfo *t)
> >  {
> > +    char *base_name = t->base_name ?
> > +                      NULL :
> > +                      g_strdup_printf("%s-base-type", t->generic_name);
> >      TypeInfo base_type_info = {
> > -        .name          = t->base_name,
> > +        .name          = t->base_name ?: base_name,
> >          .parent        = t->parent ? t->parent : TYPE_VIRTIO_PCI,
> >          .instance_size = t->instance_size,
> >          .instance_init = t->instance_init,
> > @@ -1959,21 +1955,8 @@ void virtio_pci_types_register(const 
> > VirtioPCIDeviceTypeInfo *t)
> >          },
> >      };
> >
> > -    if (!base_type_info.name) {
> > -        /* No base type -> register a single generic device type */
> > -        base_type_info.name = t->generic_name;
> > -        base_type_info.class_init = virtio_pci_generic_base_class_init;
> > -        base_type_info.interfaces = generic_type_info.interfaces;
> > -        base_type_info.abstract = false;
> > -        generic_type_info.name = NULL;
> > -        assert(!t->non_transitional_name);
> > -        assert(!t->transitional_name);
> > -    }
> > -
> >      type_register(&base_type_info);
> > -    if (generic_type_info.name) {
> > -        type_register(&generic_type_info);
> > -    }
> > +    type_register(&generic_type_info);
> 
> t->generic_name can't be NULL anymore? I thought the condition was
> done for a good reason.

My mistake.  I forgot generic_type_info.name could be NULL
because of t->generic_name was already NULL.

> 
> >
> >      if (t->non_transitional_name) {
> >          const TypeInfo non_transitional_type_info = {
> > @@ -2005,6 +1988,7 @@ void virtio_pci_types_register(const 
> > VirtioPCIDeviceTypeInfo *t)
> >          };
> >          type_register(&transitional_type_info);
> >      }
> > +    g_free(base_name);
> >  }
> >
> >  /* virtio-pci-bus */
> >
> >
> > --
> > Eduardo
> >
> 
> 
> -- 
> Marc-André Lureau

-- 
Eduardo