On Tue, Sep 14, 2021 at 08:24:51PM +0800, Wu Zongyong wrote:
> This new attribute advertises whether the vdpa device is legacy or not.
> Users can pick right virtqueue size if the vdpa device is legacy which
> doesn't support to change virtqueue size.
>
> Signed-off-by: Wu Zongyong <wuzongyong@xxxxxxxxxxxxxxxxx>
So if we are bothering with legacy, I think there are
several things to do when building the interface
- support transitional devices, that is allow userspace
to tell device it's in legacy mode
- support reporting/setting supporting endian-ness
> ---
> drivers/vdpa/vdpa.c | 6 ++++++
> drivers/virtio/virtio_vdpa.c | 7 ++++++-
> include/uapi/linux/vdpa.h | 1 +
> 3 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 1dc121a07a93..533d7f589eee 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -12,6 +12,7 @@
> #include <linux/slab.h>
> #include <linux/vdpa.h>
> #include <uapi/linux/vdpa.h>
> +#include <uapi/linux/virtio_config.h>
> #include <net/genetlink.h>
> #include <linux/mod_devicetable.h>
>
> @@ -494,6 +495,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq
> u16 max_vq_size;
> u32 device_id;
> u32 vendor_id;
> + u64 features;
> void *hdr;
> int err;
>
> @@ -508,6 +510,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq
> device_id = vdev->config->get_device_id(vdev);
> vendor_id = vdev->config->get_vendor_id(vdev);
> max_vq_size = vdev->config->get_vq_num_max(vdev);
> + features = vdev->config->get_features(vdev);
>
> err = -EMSGSIZE;
> if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev)))
> @@ -520,6 +523,9 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq
> goto msg_err;
> if (nla_put_u16(msg, VDPA_ATTR_DEV_MAX_VQ_SIZE, max_vq_size))
> goto msg_err;
> + if (features & BIT_ULL(VIRTIO_F_VERSION_1) &&
> + nla_put_flag(msg, VDPA_ATTR_DEV_VERSION_1))
> + goto msg_err;
>
> genlmsg_end(msg, hdr);
> return 0;
> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> index 72eaef2caeb1..1cba957c4cdc 100644
> --- a/drivers/virtio/virtio_vdpa.c
> +++ b/drivers/virtio/virtio_vdpa.c
> @@ -7,6 +7,7 @@
> *
> */
>
> +#include "linux/virtio_config.h"
> #include <linux/init.h>
> #include <linux/module.h>
> #include <linux/device.h>
> @@ -145,6 +146,7 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
> /* Assume split virtqueue, switch to packed if necessary */
> struct vdpa_vq_state state = {0};
> unsigned long flags;
> + bool may_reduce_num = false;
> u32 align, num;
> int err;
>
> @@ -169,10 +171,13 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
> goto error_new_virtqueue;
> }
>
> + if (ops->get_features(vdpa) & BIT_ULL(VIRTIO_F_VERSION_1))
> + may_reduce_num = true;
> +
> /* Create the vring */
> align = ops->get_vq_align(vdpa);
> vq = vring_create_virtqueue(index, num, align, vdev,
> - true, true, ctx,
> + true, may_reduce_num, ctx,
> virtio_vdpa_notify, callback, name);
> if (!vq) {
> err = -ENOMEM;
> diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> index 66a41e4ec163..ce0b74276a5b 100644
> --- a/include/uapi/linux/vdpa.h
> +++ b/include/uapi/linux/vdpa.h
> @@ -32,6 +32,7 @@ enum vdpa_attr {
> VDPA_ATTR_DEV_VENDOR_ID, /* u32 */
> VDPA_ATTR_DEV_MAX_VQS, /* u32 */
> VDPA_ATTR_DEV_MAX_VQ_SIZE, /* u16 */
> + VDPA_ATTR_DEV_VERSION_1, /* flag */
>
> /* new attributes must be added above here */
> VDPA_ATTR_MAX,
> --
> 2.31.1
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