RE: [PATCH 1/2] hw/virtio/vhost-user: don't use uninitialized variable

[Liu, Changpeng]

> -----Original Message-----
> From: Alex Bennée <alex.bennee@linaro.org>
> Sent: Tuesday, May 31, 2022 10:46 PM
> To: Liu, Changpeng <changpeng.liu@intel.com>
> Cc: qemu-devel@nongnu.org
> Subject: Re: [PATCH 1/2] hw/virtio/vhost-user: don't use uninitialized 
> variable
> 
> 
> Changpeng Liu <changpeng.liu@intel.com> writes:
> 
> > Variable `vdev` in `struct vhost_dev` will not be ready
> > until start the device, so let's not use it for the error
> > output here.
> 
> This seems to be one of the areas where vhost_user_backend_dev_init and
> vhost_dev_init do things differently. Is there any particular reason why
> we couldn't initialise hdev->vdev consistently at init time?
vhost_dev_init() set hdev->vdev to NULL, and vhost_dev_start() set it to 
VirtIODevice,
it's consistent, they are common APIs designed for vhost-kernel and vhost-user.
> 
> >
> > Fixes: 5653493 ("hw/virtio/vhost-user: don't suppress F_CONFIG when
> supported")
> >
> > Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
> > ---
> >  hw/virtio/vhost-user.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index b040c1ad2b..0594178224 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -2031,18 +2031,16 @@ static int vhost_user_backend_init(struct
> vhost_dev *dev, void *opaque,
> >          if (supports_f_config) {
> >              if (!virtio_has_feature(protocol_features,
> >                                      VHOST_USER_PROTOCOL_F_CONFIG)) {
> > -                error_setg(errp, "vhost-user device %s expecting "
> > +                error_setg(errp, "vhost-user device expecting "
> >                             "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user
> backend does "
> > -                           "not support it.", dev->vdev->name);
> > +                           "not support it.");
> >                  return -EPROTO;
> >              }
> >          } else {
> >              if (virtio_has_feature(protocol_features,
> >                                     VHOST_USER_PROTOCOL_F_CONFIG)) {
> >                  warn_reportf_err(*errp, "vhost-user backend supports "
> > -                                 "VHOST_USER_PROTOCOL_F_CONFIG for "
> > -                                 "device %s but QEMU does not.",
> > -                                 dev->vdev->name);
> > +                                 "VHOST_USER_PROTOCOL_F_CONFIG but QEMU 
> > does not.");
> >                  protocol_features &= ~(1ULL << 
> > VHOST_USER_PROTOCOL_F_CONFIG);
> >              }
> >          }
> 
> 
> --
> Alex Bennée