From 844619147c5110f335cbbbad51cda6a898c7ef33 Mon Sep 17 00:00:00 2001 From: Jonah Palmer Date: Wed, 10 Jul 2024 08:55:17 -0400 Subject: virtio: virtqueue_ordered_flush - VIRTIO_F_IN_ORDER support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add VIRTIO_F_IN_ORDER feature support for the virtqueue_flush operation. The goal of the virtqueue_ordered_flush operation when the VIRTIO_F_IN_ORDER feature has been negotiated is to write elements to the used/descriptor ring in-order and then update used_idx. The function iterates through the VirtQueueElement used_elems array in-order starting at vq->used_idx. If the element is valid (filled), the element is written to the used/descriptor ring. This process continues until we find an invalid (not filled) element. For packed VQs, the first entry (at vq->used_idx) is written to the descriptor ring last so the guest doesn't see any invalid descriptors. If any elements were written, the used_idx is updated. Signed-off-by: Jonah Palmer Message-Id: <20240710125522.4168043-5-jonah.palmer@oracle.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Acked-by: Eugenio Pérez --- hw/virtio/virtio.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 70 insertions(+), 1 deletion(-) (limited to 'hw/virtio') diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 0000a7b41c..397c261c3c 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -1023,6 +1023,73 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count) } } +static void virtqueue_ordered_flush(VirtQueue *vq) +{ + unsigned int i = vq->used_idx % vq->vring.num; + unsigned int ndescs = 0; + uint16_t old = vq->used_idx; + uint16_t new; + bool packed; + VRingUsedElem uelem; + + packed = virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED); + + if (packed) { + if (unlikely(!vq->vring.desc)) { + return; + } + } else if (unlikely(!vq->vring.used)) { + return; + } + + /* First expected in-order element isn't ready, nothing to do */ + if (!vq->used_elems[i].in_order_filled) { + return; + } + + /* Search for filled elements in-order */ + while (vq->used_elems[i].in_order_filled) { + /* + * First entry for packed VQs is written last so the guest + * doesn't see invalid descriptors. + */ + if (packed && i != vq->used_idx) { + virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false); + } else if (!packed) { + uelem.id = vq->used_elems[i].index; + uelem.len = vq->used_elems[i].len; + vring_used_write(vq, &uelem, i); + } + + vq->used_elems[i].in_order_filled = false; + ndescs += vq->used_elems[i].ndescs; + i += vq->used_elems[i].ndescs; + if (i >= vq->vring.num) { + i -= vq->vring.num; + } + } + + if (packed) { + virtqueue_packed_fill_desc(vq, &vq->used_elems[vq->used_idx], 0, true); + vq->used_idx += ndescs; + if (vq->used_idx >= vq->vring.num) { + vq->used_idx -= vq->vring.num; + vq->used_wrap_counter ^= 1; + vq->signalled_used_valid = false; + } + } else { + /* Make sure buffer is written before we update index. */ + smp_wmb(); + new = old + ndescs; + vring_used_idx_set(vq, new); + if (unlikely((int16_t)(new - vq->signalled_used) < + (uint16_t)(new - old))) { + vq->signalled_used_valid = false; + } + } + vq->inuse -= ndescs; +} + void virtqueue_flush(VirtQueue *vq, unsigned int count) { if (virtio_device_disabled(vq->vdev)) { @@ -1030,7 +1097,9 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count) return; } - if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) { + if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_IN_ORDER)) { + virtqueue_ordered_flush(vq); + } else if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) { virtqueue_packed_flush(vq, count); } else { virtqueue_split_flush(vq, count); -- cgit v1.2.3