virtio_vdpa relies on the core's synchronize_rcu() fallback for callback synchronization. That covers IRQ handlers and sections with interrupts, preemption or bottom halves disabled. virtio_vdpa does not enforce any of those contexts when a vDPA driver invokes a callback.
Add an SRCU domain per device and enter it around the virtqueue and config callbacks. Implement synchronize_cbs() with synchronize_srcu() so it covers the callbacks regardless of the calling context. SRCU uses per-CPU reader accounting, avoiding a single callback lock shared by all queues. Cover the config callback too, as virtio-pci does for its config vector. Assisted-by: LLM Signed-off-by: Karl Mehltretter <[email protected]> --- drivers/virtio/virtio_vdpa.c | 34 +++++++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c index 6bcf4567a929..f9559b6b2e0b 100644 --- a/drivers/virtio/virtio_vdpa.c +++ b/drivers/virtio/virtio_vdpa.c @@ -12,6 +12,7 @@ #include <linux/device.h> #include <linux/kernel.h> #include <linux/slab.h> +#include <linux/srcu.h> #include <linux/uuid.h> #include <linux/group_cpus.h> #include <linux/virtio.h> @@ -27,6 +28,7 @@ struct virtio_vdpa_device { struct virtio_device vdev; struct vdpa_device *vdpa; + struct srcu_struct cb_srcu; u64 features; }; @@ -114,8 +116,11 @@ static bool virtio_vdpa_notify_with_data(struct virtqueue *vq) static irqreturn_t virtio_vdpa_config_cb(void *private) { struct virtio_vdpa_device *vd_dev = private; + int idx; + idx = srcu_read_lock(&vd_dev->cb_srcu); virtio_config_changed(&vd_dev->vdev); + srcu_read_unlock(&vd_dev->cb_srcu, idx); return IRQ_HANDLED; } @@ -123,8 +128,22 @@ static irqreturn_t virtio_vdpa_config_cb(void *private) static irqreturn_t virtio_vdpa_virtqueue_cb(void *private) { struct virtqueue *vq = private; + struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vq->vdev); + irqreturn_t ret; + int idx; + + idx = srcu_read_lock(&vd_dev->cb_srcu); + ret = vring_interrupt(0, vq); + srcu_read_unlock(&vd_dev->cb_srcu, idx); + + return ret; +} + +static void virtio_vdpa_synchronize_cbs(struct virtio_device *vdev) +{ + struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vdev); - return vring_interrupt(0, vq); + synchronize_srcu(&vd_dev->cb_srcu); } static struct virtqueue * @@ -440,6 +459,7 @@ static const struct virtio_config_ops virtio_vdpa_config_ops = { .reset = virtio_vdpa_reset, .find_vqs = virtio_vdpa_find_vqs, .del_vqs = virtio_vdpa_del_vqs, + .synchronize_cbs = virtio_vdpa_synchronize_cbs, .get_features = virtio_vdpa_get_features, .finalize_features = virtio_vdpa_finalize_features, .bus_name = virtio_vdpa_bus_name, @@ -454,6 +474,7 @@ static void virtio_vdpa_release_dev(struct device *_d) struct virtio_vdpa_device *vd_dev = container_of(vdev, struct virtio_vdpa_device, vdev); + cleanup_srcu_struct(&vd_dev->cb_srcu); kfree(vd_dev); } @@ -467,6 +488,11 @@ static int virtio_vdpa_probe(struct vdpa_device *vdpa) if (!vd_dev) return -ENOMEM; + if (init_srcu_struct(&vd_dev->cb_srcu)) { + kfree(vd_dev); + return -ENOMEM; + } + vd_dev->vdev.dev.parent = vdpa->map ? &vdpa->dev : vdpa_get_map(vdpa).dma_dev; vd_dev->vdev.dev.release = virtio_vdpa_release_dev; @@ -489,10 +515,12 @@ static int virtio_vdpa_probe(struct vdpa_device *vdpa) return 0; err: - if (reg_dev) + if (reg_dev) { put_device(&vd_dev->vdev.dev); - else + } else { + cleanup_srcu_struct(&vd_dev->cb_srcu); kfree(vd_dev); + } return ret; } -- 2.39.5 (Apple Git-154)
