On Thu, May 03, 2018 at 10:59:55AM +0800, Tiwei Bie wrote:
> This patch introduces the support for VIRTIO_F_IO_BARRIER.
> When this feature is negotiated, driver will use the barriers
> suitable for hardware devices.
>
> Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx>
Thanks!
> ---
> drivers/virtio/virtio_ring.c | 5 +++++
> include/uapi/linux/virtio_config.h | 8 +++++++-
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 21d464a29cf8..edb565643bf4 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -996,6 +996,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> !context;
> vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
>
> + if (virtio_has_feature(vdev, VIRTIO_F_IO_BARRIER))
> + vq->weak_barriers = false;
> +
> /* No callback? Tell other side not to bother us. */
> if (!callback) {
> vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
One issue worth looking at is that at least on Intel strong barriers are
actually typically overkill. We should probably switch weak_barriers ==
false case over to dma barriers.
> @@ -1164,6 +1167,8 @@ void vring_transport_features(struct virtio_device *vdev)
> break;
> case VIRTIO_F_IOMMU_PLATFORM:
> break;
> + case VIRTIO_F_IO_BARRIER:
> + break;
> default:
> /* We don't understand this bit. */
> __virtio_clear_bit(vdev, i);
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index 308e2096291f..6ca8d24bf468 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
Any virtio UAPI changes must be CC'd to one of the virtio TC mailing lists
(subscriber-only, sorry about that).
> @@ -49,7 +49,7 @@
> * transport being used (eg. virtio_ring), the rest are per-device feature
> * bits. */
> #define VIRTIO_TRANSPORT_F_START 28
> -#define VIRTIO_TRANSPORT_F_END 34
> +#define VIRTIO_TRANSPORT_F_END 38
>
> #ifndef VIRTIO_CONFIG_NO_LEGACY
> /* Do we get callbacks when the ring is completely used, even if we've
> @@ -71,4 +71,10 @@
> * this is for compatibility with legacy systems.
> */
> #define VIRTIO_F_IOMMU_PLATFORM 33
> +
> +/*
> + * If clear - driver may use barriers suitable for CPU cores.
> + * If set - driver must use barriers suitable for hardware devices.
> + */
> +#define VIRTIO_F_IO_BARRIER 37
> #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
Why 37? I'd use 34 I think.
> --
> 2.11.0
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