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Subject[PATCH v1] virtio: support VIRTIO_F_IO_BARRIER
Date
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@intel.com>
---
This patch depends on below proposal for virtio-spec:
https://lists.oasis-open.org/archives/virtio-dev/201805/msg00019.html

This patch also depends on below patch:
https://lkml.org/lkml/2018/4/19/789

RFC -> v1:
- Address the changes in the proposal;

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;
@@ -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..9fb519a9df28 100644
--- a/include/uapi/linux/virtio_config.h
+++ b/include/uapi/linux/virtio_config.h
@@ -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 37

#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 36
#endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
--
2.11.0
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