On Sat, Oct 21, 2023 at 5:28 PM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
>
> Using .compat_reset op from the previous patch, the buggy .reset
> behaviour can be kept as-is on older userspace apps, which don't ack the
> IOTLB_PERSIST backend feature. As this compatibility quirk is limited to
> those drivers that used to be buggy in the past, it won't affect change
> the behaviour or affect ABI on the setups with API compliant driver.
>
> The separation of .compat_reset from the regular .reset allows
> vhost-vdpa able to know which driver had broken behaviour before, so it
> can apply the corresponding compatibility quirk to the individual driver
> whenever needed. Compared to overloading the existing .reset with
> flags, .compat_reset won't cause any extra burden to the implementation
> of every compliant driver.
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
> ---
> drivers/vhost/vdpa.c | 17 +++++++++++++----
> drivers/virtio/virtio_vdpa.c | 2 +-
> include/linux/vdpa.h | 7 +++++--
> 3 files changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index acc7c74ba7d6..9ce40003793b 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -227,13 +227,22 @@ static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
> irq_bypass_unregister_producer(&vq->call_ctx.producer);
> }
>
> -static int vhost_vdpa_reset(struct vhost_vdpa *v)
> +static int _compat_vdpa_reset(struct vhost_vdpa *v)
> {
> struct vdpa_device *vdpa = v->vdpa;
> + u32 flags = 0;
>
> - v->in_batch = 0;
> + flags |= !vhost_backend_has_feature(v->vdev.vqs[0],
> + VHOST_BACKEND_F_IOTLB_PERSIST) ?
> + VDPA_RESET_F_CLEAN_MAP : 0;
> +
> + return vdpa_reset(vdpa, flags);
> +}
>
> - return vdpa_reset(vdpa);
> +static int vhost_vdpa_reset(struct vhost_vdpa *v)
> +{
> + v->in_batch = 0;
> + return _compat_vdpa_reset(v);
> }
>
> static long vhost_vdpa_bind_mm(struct vhost_vdpa *v)
> @@ -312,7 +321,7 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp)
> vhost_vdpa_unsetup_vq_irq(v, i);
>
> if (status == 0) {
> - ret = vdpa_reset(vdpa);
> + ret = _compat_vdpa_reset(v);
> if (ret)
> return ret;
> } else
> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> index 06ce6d8c2e00..8d63e5923d24 100644
> --- a/drivers/virtio/virtio_vdpa.c
> +++ b/drivers/virtio/virtio_vdpa.c
> @@ -100,7 +100,7 @@ static void virtio_vdpa_reset(struct virtio_device *vdev)
> {
> struct vdpa_device *vdpa = vd_get_vdpa(vdev);
>
> - vdpa_reset(vdpa);
> + vdpa_reset(vdpa, 0);
> }
>
> static bool virtio_vdpa_notify(struct virtqueue *vq)
> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> index 6b8cbf75712d..db15ac07f8a6 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -519,14 +519,17 @@ static inline struct device *vdpa_get_dma_dev(struct vdpa_device *vdev)
> return vdev->dma_dev;
> }
>
> -static inline int vdpa_reset(struct vdpa_device *vdev)
> +static inline int vdpa_reset(struct vdpa_device *vdev, u32 flags)
> {
> const struct vdpa_config_ops *ops = vdev->config;
> int ret;
>
> down_write(&vdev->cf_lock);
> vdev->features_valid = false;
> - ret = ops->reset(vdev);
> + if (ops->compat_reset && flags)
> + ret = ops->compat_reset(vdev, flags);
> + else
> + ret = ops->reset(vdev);
Instead of inventing a new API that carries the flags. Tweak the
existing one seems to be simpler and better?
As compat_reset(vdev, 0) == reset(vdev)
Then you don't need the switch in the parent as well
+static int vdpasim_reset(struct vdpa_device *vdpa)
+{
+ return vdpasim_compat_reset(vdpa, 0);
+}
Thanks
> up_write(&vdev->cf_lock);
> return ret;
> }
> --
> 2.39.3
>
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