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authorTiwei Bie2019-01-23 10:50:26 +0100
committerMichael S. Tsirkin2019-01-24 16:15:42 +0100
commit45383fb0f42db3945ac6cc658704706cdae19528 (patch)
treeb25548cd2da896976f1cf718b4b97fd67efece92
parentLinux 5.0-rc3 (diff)
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virtio: support VIRTIO_F_ORDER_PLATFORM
This patch introduces the support for VIRTIO_F_ORDER_PLATFORM. If this feature is negotiated, the driver must use the barriers suitable for hardware devices. Otherwise, the device and driver are assumed to be implemented in software, that is they can be assumed to run on identical CPUs in an SMP configuration. Thus a weaker form of memory barriers is sufficient to yield better performance. It is recommended that an add-in card based PCI device offers this feature for portability. The device will fail to operate further or will operate in a slower emulation mode if this feature is offered but not accepted. Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--drivers/virtio/virtio_ring.c8
-rw-r--r--include/uapi/linux/virtio_config.h6
2 files changed, 14 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..27d3f057493e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1609,6 +1609,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
+ vq->weak_barriers = false;
+
vq->packed.ring_dma_addr = ring_dma_addr;
vq->packed.driver_event_dma_addr = driver_event_dma_addr;
vq->packed.device_event_dma_addr = device_event_dma_addr;
@@ -2079,6 +2082,9 @@ 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_ORDER_PLATFORM))
+ vq->weak_barriers = false;
+
vq->split.queue_dma_addr = 0;
vq->split.queue_size_in_bytes = 0;
@@ -2213,6 +2219,8 @@ void vring_transport_features(struct virtio_device *vdev)
break;
case VIRTIO_F_RING_PACKED:
break;
+ case VIRTIO_F_ORDER_PLATFORM:
+ 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 1196e1c1d4f6..ff8e7dc9d4dd 100644
--- a/include/uapi/linux/virtio_config.h
+++ b/include/uapi/linux/virtio_config.h
@@ -79,6 +79,12 @@
#define VIRTIO_F_RING_PACKED 34
/*
+ * This feature indicates that memory accesses by the driver and the
+ * device are ordered in a way described by the platform.
+ */
+#define VIRTIO_F_ORDER_PLATFORM 36
+
+/*
* Does the device support Single Root I/O Virtualization?
*/
#define VIRTIO_F_SR_IOV 37