Messages in this thread | | | Subject | Re: [RFC] virtio: support VIRTIO_F_IO_BARRIER | From | Jason Wang <> | Date | Thu, 3 May 2018 17:09:44 +0800 |
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On 2018年05月03日 16:30, Tiwei Bie wrote: > On Thu, May 03, 2018 at 03:30:03PM +0800, Jason Wang wrote: >> On 2018年05月03日 10:59, 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@intel.com> >>> --- >>> 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..6ca8d24bf468 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 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 */ >> Hi: >> >> I believe this depends on Michael's patch of >> >> "[PATCH] virtio_ring: switch to dma_XX barriers for rpmsg" >> >> ? >> >> Thanks > We already have below commit and some other related commits > in the tree: > > 7b21e34fd1c2 ("virtio: harsher barriers for rpmsg.") > > They should have already guaranteed that virtio_Xmb() will > be OK for hardware devices when vq->weak_barriers is false. > If my understanding is correct, the barriers used in this > case are overkill. So Michael's patch is to make the barriers > weaker (or better). > > Best regards, > Tiwei Bie
Well, I think we need dma barriers for some platforms according to previous discussion? Without Michael's patch, we won't use any dma barriers in fact for virtio.
Thanks
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