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Tsirkin" To: qemu-devel@nongnu.org Cc: Peter Maydell , Jonah Palmer , Eugenio =?utf-8?b?UMOpcmV6?= Subject: [PULL v2 25/61] virtio: virtqueue_ordered_flush - VIRTIO_F_IN_ORDER support Message-ID: <844619147c5110f335cbbbad51cda6a898c7ef33.1721731723.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.133, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Jonah Palmer 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(-) 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);