Re: [PATCH] hw/virtio: Have virtio_bus_get_vdev_bad_features() return 64-bit value

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 24, 2021 at 08:21:48PM +0200, Philippe Mathieu-Daudé wrote:
> On 5/23/21 10:07 AM, Michael S. Tsirkin wrote:
> > On Thu, May 20, 2021 at 12:28:22PM +0200, Philippe Mathieu-Daudé wrote:
> >> In commit 019a3edbb25 ("virtio: make features 64bit wide") we
> >> increased the 'features' field to 64-bit, but forgot to update
> >> the virtio_bus_get_vdev_bad_features() helper. The 'bad features'
> >> are truncated to 32-bit. The virtio_net_bad_features() handler
> >> from the virtio-net devices is potentially affected.
> > 
> > I'm fine with increasing it for consistency, but bad features
> > are all legacy things aren't they? So there isn't a functional
> > issue ... or did I miss anything?
> 
> Are you saying all bad legacy features are < 32-bit and there is no
> potential problem?

I think so yes. I agree with the change, I jus think
it's cosmetic and the commit log should say so.

> > 
> >>
> >> Have the virtio_bus_get_vdev_bad_features() helper return the
> >> full 64-bit value.
> >>
> >> Cc: qemu-stable@nongnu.org
> >> Fixes: 019a3edbb25 ("virtio: make features 64bit wide")
> >> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >> ---
> >>  include/hw/virtio/virtio-bus.h | 2 +-
> >>  hw/virtio/virtio-bus.c         | 2 +-
> >>  2 files changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
> >> index ef8abe49c5a..f9955ff577a 100644
> >> --- a/include/hw/virtio/virtio-bus.h
> >> +++ b/include/hw/virtio/virtio-bus.h
> >> @@ -122,7 +122,7 @@ uint16_t virtio_bus_get_vdev_id(VirtioBusState *bus);
> >>  /* Get the config_len field of the plugged device. */
> >>  size_t virtio_bus_get_vdev_config_len(VirtioBusState *bus);
> >>  /* Get bad features of the plugged device. */
> >> -uint32_t virtio_bus_get_vdev_bad_features(VirtioBusState *bus);
> >> +uint64_t virtio_bus_get_vdev_bad_features(VirtioBusState *bus);
> >>  /* Get config of the plugged device. */
> >>  void virtio_bus_get_vdev_config(VirtioBusState *bus, uint8_t *config);
> >>  /* Set config of the plugged device. */
> >> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> >> index 859978d2487..25a2b68a234 100644
> >> --- a/hw/virtio/virtio-bus.c
> >> +++ b/hw/virtio/virtio-bus.c
> >> @@ -134,7 +134,7 @@ size_t virtio_bus_get_vdev_config_len(VirtioBusState *bus)
> >>  }
> >>  
> >>  /* Get bad features of the plugged device. */
> >> -uint32_t virtio_bus_get_vdev_bad_features(VirtioBusState *bus)
> >> +uint64_t virtio_bus_get_vdev_bad_features(VirtioBusState *bus)
> >>  {
> >>      VirtIODevice *vdev = virtio_bus_get_device(bus);
> >>      VirtioDeviceClass *k;
> >> -- 
> >> 2.26.3
> >