From 45383fb0f42db3945ac6cc658704706cdae19528 Mon Sep 17 00:00:00 2001 From: Tiwei Bie Date: Wed, 23 Jan 2019 17:50:26 +0800 Subject: 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 Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/uapi/linux/virtio_config.h | 6 ++++++ 2 files changed, 14 insertions(+) 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 @@ -78,6 +78,12 @@ /* This feature indicates support for the packed virtqueue layout. */ #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? */ -- cgit v1.2.3 From 9c0644ee4aa8792f1e60a2b014b4710faaddafeb Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Fri, 1 Feb 2019 17:13:57 -0500 Subject: virtio: drop internal struct from UAPI There's no reason to expose struct vring_packed in UAPI - if we do we won't be able to change or drop it, and it's not part of any interface. Let's move it to virtio_ring.c Cc: Tiwei Bie Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_ring.c | 7 ++++++- include/uapi/linux/virtio_ring.h | 10 ---------- 2 files changed, 6 insertions(+), 11 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 27d3f057493e..a0b07c331255 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -152,7 +152,12 @@ struct vring_virtqueue { /* Available for packed ring */ struct { /* Actual memory layout for this queue. */ - struct vring_packed vring; + struct { + unsigned int num; + struct vring_packed_desc *desc; + struct vring_packed_desc_event *driver; + struct vring_packed_desc_event *device; + } vring; /* Driver ring wrap counter. */ bool avail_wrap_counter; diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h index 2414f8af26b3..4c4e24c291a5 100644 --- a/include/uapi/linux/virtio_ring.h +++ b/include/uapi/linux/virtio_ring.h @@ -213,14 +213,4 @@ struct vring_packed_desc { __le16 flags; }; -struct vring_packed { - unsigned int num; - - struct vring_packed_desc *desc; - - struct vring_packed_desc_event *driver; - - struct vring_packed_desc_event *device; -}; - #endif /* _UAPI_LINUX_VIRTIO_RING_H */ -- cgit v1.2.3