On Thu, Jan 29, 2026 at 2:17 AM Jason Wang <[email protected]> wrote: > > On Wed, Jan 28, 2026 at 8:45 PM Eugenio Pérez <[email protected]> wrote: > > > > The vduse_vdpa_set_vq_ready can be called in the lifetime of the device > > well after initial setup, and the device can read it afterwards. > > > > Ensure that reads and writes to vq->ready are SMP safe so that the > > caller can trust that virtqueue kicks and calls behave as expected > > immediately after the operation returns. > > > > Signed-off-by: Eugenio Pérez <[email protected]> > > --- > > drivers/vdpa/vdpa_user/vduse_dev.c | 34 +++++++++++++++++++++++------- > > 1 file changed, 26 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c > > b/drivers/vdpa/vdpa_user/vduse_dev.c > > index 73d1d517dc6c..a4963aaf9332 100644 > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c > > @@ -460,6 +460,24 @@ static __poll_t vduse_dev_poll(struct file *file, > > poll_table *wait) > > return mask; > > } > > > > +static bool vduse_vq_get_ready(const struct vduse_virtqueue *vq) > > +{ > > + /* > > + * Paired with vduse_vq_set_ready smp_store, as the driver may > > modify > > + * it while the VDUSE instance is reading it. > > + */ > > + return smp_load_acquire(&vq->ready); > > +} > > + > > +static void vduse_vq_set_ready(struct vduse_virtqueue *vq, bool ready) > > +{ > > + /* > > + * Paired with vduse_vq_get_ready smp_load, as the driver may modify > > + * it while the VDUSE instance is reading it. > > + */ > > + smp_store_release(&vq->ready, ready); > > Assuming this is not used in the datapath, I wonder if we can simply > use vq_lock mutex. >
The function vduse_vq_set/get_ready are not in the datapath, but vduse_vq_kick and vduse_vq_signal_irqfd are. I'm ok if you want to switch to vq_mutex if you want though, maybe it's even comparable with the cost of the ioctls or eventfd signaling.
