On Tue, Mar 3, 2026 at 8:26 AM Jason Wang <[email protected]> wrote:
>
> On Wed, Feb 11, 2026 at 8:02 PM Eugenio Pérez <[email protected]> wrote:
> >
> > Implement suspend operation for vduse devices, so vhost-vdpa will offer
> > that backend feature and userspace can effectively suspend the device.
> >
> > This is a must before get virtqueue indexes (base) for live migration,
> > since the device could modify them after userland gets them.
> >
> > Signed-off-by: Eugenio Pérez <[email protected]>
> > ---
> > This series depends on
> > https://lore.kernel.org/lkml/[email protected]
> > ---
> > drivers/vdpa/vdpa_user/vduse_dev.c | 86 +++++++++++++++++++++++++++++-
> > include/uapi/linux/vduse.h | 4 ++
> > 2 files changed, 88 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
> > b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 59d9c4718d86..bdcc114e2710 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -54,7 +54,8 @@
> > #define IRQ_UNBOUND -1
> >
> > /* Supported VDUSE features */
> > -static const uint64_t vduse_features = BIT_U64(VDUSE_F_QUEUE_READY);
> > +static const uint64_t vduse_features = BIT_U64(VDUSE_F_QUEUE_READY) |
> > + BIT_U64(VDUSE_F_SUSPEND);
> >
> > /*
> > * VDUSE instance have not asked the vduse API version, so assume 0.
> > @@ -85,6 +86,7 @@ struct vduse_virtqueue {
> > int irq_effective_cpu;
> > struct cpumask irq_affinity;
> > struct kobject kobj;
> > + struct vduse_dev *dev;
> > };
> >
> > struct vduse_dev;
> > @@ -134,6 +136,7 @@ struct vduse_dev {
> > int minor;
> > bool broken;
> > bool connected;
> > + bool suspended;
> > u64 api_version;
> > u64 device_features;
> > u64 driver_features;
> > @@ -480,6 +483,7 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> >
> > down_write(&dev->rwsem);
> >
> > + dev->suspended = false;
> > dev->status = 0;
> > dev->driver_features = 0;
> > dev->generation++;
> > @@ -559,6 +563,10 @@ static void vduse_vdpa_kick_vq(struct vdpa_device
> > *vdpa, u16 idx)
> > struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> > struct vduse_virtqueue *vq = dev->vqs[idx];
> >
> > + guard(rwsem_read)(&vq->dev->rwsem);
> > + if (vq->dev->suspended)
> > + return;
> > +
> > if (!eventfd_signal_allowed()) {
> > schedule_work(&vq->kick);
> > return;
> > @@ -896,6 +904,27 @@ static int vduse_vdpa_set_map(struct vdpa_device *vdpa,
> > return 0;
> > }
> >
> > +static int vduse_vdpa_suspend(struct vdpa_device *vdpa)
> > +{
> > + struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> > + struct vduse_dev_msg msg = { 0 };
> > + int ret;
> > +
> > + msg.req.type = VDUSE_SUSPEND;
> > +
> > + ret = vduse_dev_msg_sync(dev, &msg);
> > + if (ret == 0) {
> > + scoped_guard(rwsem_write, &dev->rwsem)
> > + dev->suspended = true;
> > +
> > + cancel_work_sync(&dev->inject);
> > + for (u32 i = 0; i < dev->vq_num; i++)
> > + cancel_work_sync(&dev->vqs[i]->inject);
>
> Should we cancel those before msy sync?
>
The only condition is that the driver must not see interrupts from the
moment the ioctl returns.
Also, disabling it before the msg returns would add complexity because
it needs to be reenabled & call the driver if it falis. Or am I
missing something it adds?
TBH this is more of a hardening than something the VDUSE driver should
do. We could even move to the vdpa core.
> > + }
> > +
> > + return ret;
> > +}
> > +
> > static void vduse_vdpa_free(struct vdpa_device *vdpa)
> > {
> > struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> > @@ -937,6 +966,41 @@ static const struct vdpa_config_ops
> > vduse_vdpa_config_ops = {
> > .free = vduse_vdpa_free,
> > };
> >
> > +static const struct vdpa_config_ops vduse_vdpa_config_ops_with_suspend = {
> > + .set_vq_address = vduse_vdpa_set_vq_address,
> > + .kick_vq = vduse_vdpa_kick_vq,
> > + .set_vq_cb = vduse_vdpa_set_vq_cb,
> > + .set_vq_num = vduse_vdpa_set_vq_num,
> > + .get_vq_size = vduse_vdpa_get_vq_size,
> > + .get_vq_group = vduse_get_vq_group,
> > + .set_vq_ready = vduse_vdpa_set_vq_ready,
> > + .get_vq_ready = vduse_vdpa_get_vq_ready,
> > + .set_vq_state = vduse_vdpa_set_vq_state,
> > + .get_vq_state = vduse_vdpa_get_vq_state,
> > + .get_vq_align = vduse_vdpa_get_vq_align,
> > + .get_device_features = vduse_vdpa_get_device_features,
> > + .set_driver_features = vduse_vdpa_set_driver_features,
> > + .get_driver_features = vduse_vdpa_get_driver_features,
> > + .set_config_cb = vduse_vdpa_set_config_cb,
> > + .get_vq_num_max = vduse_vdpa_get_vq_num_max,
> > + .get_device_id = vduse_vdpa_get_device_id,
> > + .get_vendor_id = vduse_vdpa_get_vendor_id,
> > + .get_status = vduse_vdpa_get_status,
> > + .set_status = vduse_vdpa_set_status,
> > + .get_config_size = vduse_vdpa_get_config_size,
> > + .get_config = vduse_vdpa_get_config,
> > + .set_config = vduse_vdpa_set_config,
> > + .get_generation = vduse_vdpa_get_generation,
> > + .set_vq_affinity = vduse_vdpa_set_vq_affinity,
> > + .get_vq_affinity = vduse_vdpa_get_vq_affinity,
> > + .reset = vduse_vdpa_reset,
> > + .set_map = vduse_vdpa_set_map,
> > + .set_group_asid = vduse_set_group_asid,
> > + .get_vq_map = vduse_get_vq_map,
> > + .suspend = vduse_vdpa_suspend,
>
> We can have a
>
> if (suspend_is_supported)
> ...
>
> to avoid having a new set of config ops?
>
It complicates the code of vhost_vdpa in my opinion.
Currently, it is:
if (ops->suspend)
And that would move to something like:
if (ops->suspend) {
if (ops->suspend_is_supported && !ops->suspend_is_supported(dev)) {
return; // CANNOT SUSPEND
}
ops->suspend(dev)
}
Another option I considered is to follow mlx5's approach and have one
set of ops per device. But I think duplicating the vdpa_ops in the
data section is the cleanest approach. Let me know if you think we
should go with suspend_is_supported callback instead.
> > + .free = vduse_vdpa_free,
> > +};
> > +
> > static void vduse_dev_sync_single_for_device(union virtio_map token,
> > dma_addr_t dma_addr, size_t
> > size,
> > enum dma_data_direction dir)
> > @@ -1148,6 +1212,10 @@ static void vduse_dev_irq_inject(struct work_struct
> > *work)
> > {
> > struct vduse_dev *dev = container_of(work, struct vduse_dev,
> > inject);
> >
> > + guard(rwsem_read)(&dev->rwsem);
> > + if (dev->suspended)
> > + return;
>
> Device can still modify memory, so I wonder how much this can help.
>
Do you prefer me to remove this guard?
> > +
> > spin_lock_bh(&dev->irq_lock);
> > if (dev->config_cb.callback)
> > dev->config_cb.callback(dev->config_cb.private);
> > @@ -1159,6 +1227,10 @@ static void vduse_vq_irq_inject(struct work_struct
> > *work)
> > struct vduse_virtqueue *vq = container_of(work,
> > struct vduse_virtqueue, inject);
> >
> > + guard(rwsem_read)(&vq->dev->rwsem);
> > + if (vq->dev->suspended)
> > + return;
> > +
> > spin_lock_bh(&vq->irq_lock);
> > if (vq->ready && vq->cb.callback)
> > vq->cb.callback(vq->cb.private);
> > @@ -1189,6 +1261,9 @@ static int vduse_dev_queue_irq_work(struct vduse_dev
> > *dev,
> > int ret = -EINVAL;
> >
> > down_read(&dev->rwsem);
> > + if (dev->suspended)
> > + return ret;
> > +
> > if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> > goto unlock;
> >
> > @@ -1839,6 +1914,7 @@ static int vduse_dev_init_vqs(struct vduse_dev *dev,
> > u32 vq_align, u32 vq_num)
> > }
> >
> > dev->vqs[i]->index = i;
> > + dev->vqs[i]->dev = dev;
> > dev->vqs[i]->irq_effective_cpu = IRQ_UNBOUND;
> > INIT_WORK(&dev->vqs[i]->inject, vduse_vq_irq_inject);
> > INIT_WORK(&dev->vqs[i]->kick, vduse_vq_kick_work);
> > @@ -2311,12 +2387,18 @@ static struct vduse_mgmt_dev *vduse_mgmt;
> > static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
> > {
> > struct vduse_vdpa *vdev;
> > + const struct vdpa_config_ops *ops;
> >
> > if (dev->vdev)
> > return -EEXIST;
> >
> > + if (dev->vduse_features & BIT_U64(VDUSE_F_SUSPEND))
> > + ops = &vduse_vdpa_config_ops_with_suspend;
> > + else
> > + ops = &vduse_vdpa_config_ops;
> > +
> > vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> > - &vduse_vdpa_config_ops, &vduse_map_ops,
> > + ops, &vduse_map_ops,
> > dev->ngroups, dev->nas, name, true);
> > if (IS_ERR(vdev))
> > return PTR_ERR(vdev);
> > diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> > index d39734cef6d3..95b93bc6bac5 100644
> > --- a/include/uapi/linux/vduse.h
> > +++ b/include/uapi/linux/vduse.h
> > @@ -21,6 +21,9 @@
> > /* The VDUSE instance expects a request for vq ready */
> > #define VDUSE_F_QUEUE_READY 0
> >
> > +/* The VDUSE instance expects a request for suspend */
> > +#define VDUSE_F_SUSPEND 1
> > +
> > /*
> > * Get the version of VDUSE API that kernel supported (VDUSE_API_VERSION).
> > * This is used for future extension.
> > @@ -338,6 +341,7 @@ enum vduse_req_type {
> > VDUSE_UPDATE_IOTLB,
> > VDUSE_SET_VQ_GROUP_ASID,
> > VDUSE_SET_VQ_READY,
> > + VDUSE_SUSPEND,
> > };
> >
> > /**
> > --
> > 2.53.0
> >
>
> Thanks
>
