From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH 08/18] virtio_ring: support for used_event idx feature Date: Wed, 4 May 2011 23:51:38 +0300 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Krishna Kumar , Carsten Otte , lguest@lists.ozlabs.org, Shirley Ma , kvm@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, habanero@linux.vnet.ibm.com, Heiko Carstens , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, steved@us.ibm.com, Christian Borntraeger , Tom Lendacky , Martin Schwidefsky , linux390@de.ibm.com To: linux-kernel@vger.kernel.org Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org Add support for the used_event idx feature: when enabling interrupts, publish the current avail index value to the host so that we get interrupts on the next update. Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_ring.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 507d6eb..3a3ed75 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -320,6 +320,14 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) ret = vq->data[i]; detach_buf(vq, i); vq->last_used_idx++; + /* If we expect an interrupt for the next entry, tell host + * by writing event index and flush out the write before + * the read in the next get_buf call. */ + if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) { + vring_used_event(&vq->vring) = vq->last_used_idx; + virtio_mb(); + } + END_USE(vq); return ret; } @@ -341,7 +349,11 @@ bool virtqueue_enable_cb(struct virtqueue *_vq) /* We optimistically turn back on interrupts, then check if there was * more to do. */ + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to + * either clear the flags bit or point the event index at the next + * entry. Always do both to keep code simple. */ vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; + vring_used_event(&vq->vring) = vq->last_used_idx; virtio_mb(); if (unlikely(more_used(vq))) { END_USE(vq); @@ -468,6 +480,8 @@ void vring_transport_features(struct virtio_device *vdev) break; case VIRTIO_RING_F_INDIRECT_DESC: break; + case VIRTIO_RING_F_USED_EVENT_IDX: + break; default: /* We don't understand this bit. */ clear_bit(i, vdev->features); -- 1.7.5.53.gc233e