On Fri, Jan 30, 2026 at 3:17 AM Jason Wang <[email protected]> wrote: > > On Thu, Jan 29, 2026 at 2:26 PM Eugenio Perez Martin > <[email protected]> wrote: > > > > On Thu, Jan 29, 2026 at 3:12 AM Jason Wang <[email protected]> wrote: > > > > > > On Wed, Jan 28, 2026 at 8:45 PM Eugenio Pérez <[email protected]> wrote: > > > > > > > > Add the VDUSE_F_QUEUE_READY feature flag. This allows the kernel module > > > > to explicitly signal userspace when a specific virtqueue has been > > > > enabled. > > > > > > > > In scenarios like Live Migration of VirtIO net devices, the dataplane > > > > starts after the control virtqueue allowing QEMU to apply configuration > > > > in the destination device. > > > > > > > > Signed-off-by: Eugenio Pérez <[email protected]> > > > > --- > > > > drivers/vdpa/vdpa_user/vduse_dev.c | 28 +++++++++++++++++++++++++++- > > > > include/uapi/linux/vduse.h | 19 +++++++++++++++++++ > > > > 2 files changed, 46 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c > > > > b/drivers/vdpa/vdpa_user/vduse_dev.c > > > > index e7da69c2ad71..1d93b540db4d 100644 > > > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c > > > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c > > > > @@ -9,6 +9,7 @@ > > > > */ > > > > > > > > #include "linux/virtio_net.h" > > > > +#include <linux/bits.h> > > > > #include <linux/cleanup.h> > > > > #include <linux/init.h> > > > > #include <linux/module.h> > > > > @@ -53,7 +54,7 @@ > > > > #define IRQ_UNBOUND -1 > > > > > > > > /* Supported VDUSE features */ > > > > -static const uint64_t vduse_features; > > > > +static const uint64_t vduse_features = BIT_U64(VDUSE_F_QUEUE_READY); > > > > > > > > /* > > > > * VDUSE instance have not asked the vduse API version, so assume 0. > > > > @@ -120,6 +121,7 @@ struct vduse_dev { > > > > char *name; > > > > struct mutex lock; > > > > spinlock_t msg_lock; > > > > + u64 vduse_features; > > > > u64 msg_unique; > > > > u32 msg_timeout; > > > > wait_queue_head_t waitq; > > > > @@ -619,7 +621,30 @@ static void vduse_vdpa_set_vq_ready(struct > > > > vdpa_device *vdpa, > > > > { > > > > struct vduse_dev *dev = vdpa_to_vduse(vdpa); > > > > struct vduse_virtqueue *vq = dev->vqs[idx]; > > > > + struct vduse_dev_msg msg = { 0 }; > > > > + int r; > > > > + > > > > + if (!(dev->vduse_features & BIT_U64(VDUSE_F_QUEUE_READY))) > > > > + goto out; > > > > + > > > > + msg.req.type = VDUSE_SET_VQ_READY; > > > > + msg.req.vq_ready.num = idx; > > > > + msg.req.vq_ready.ready = !!ready; > > > > + > > > > + r = vduse_dev_msg_sync(dev, &msg); > > > > > > > > + if (r < 0) { > > > > + dev_dbg(&vdpa->dev, "device refuses to set vq %u ready > > > > %u", > > > > + idx, ready); > > > > + > > > > + /* We can't do better than break the device in this > > > > case */ > > > > + spin_lock(&dev->msg_lock); > > > > + vduse_dev_broken(dev); > > > > > > This has been done by vduse_dev_msg_sync(). > > > > > > > This is done by msg_sync() when userland does not reply in a > > timeframe, but not when userland replies with VDUSE_REQ_RESULT_FAILED. > > Should I add a comment? > > If this is not specific to Q_READY, I think we need to move it to > msg_sync() as well. >
It's specific to Q_READY for me, as it's the request that returns void and has no possibility to inform of an error. The VDUSE userland instance could reply to other requests with REQ_RESULT_FAILED and the driver still has capacity to recover from the failure. If we always break the device on every request fail, we deny that possibility.
