diff options
author | Vincenzo Maffione <v.maffione@gmail.com> | 2016-01-31 11:29:06 +0100 |
---|---|---|
committer | Timothy Pearson <tpearson@raptorengineering.com> | 2019-11-29 19:31:48 -0600 |
commit | 315291e025e992536c6a8fb28885e8881c24d8b0 (patch) | |
tree | 06454a24e1afebc5b966768083d82c52ae89094d | |
parent | 89eeda99af76e85acc2e6afe56c2451b8375f25b (diff) | |
download | hqemu-315291e025e992536c6a8fb28885e8881c24d8b0.zip hqemu-315291e025e992536c6a8fb28885e8881c24d8b0.tar.gz |
virtio: combine write of an entry into used ring
Fill in an element of the used ring with a single combined access to the
guest physical memory, rather than using two separated accesses.
This reduces the overhead due to expensive address translation.
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Message-Id: <e4a89a767a4a92cbb6bcc551e151487eb36e1722.1450218353.git.v.maffione@gmail.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r-- | hw/virtio/virtio.c | 25 |
1 files changed, 12 insertions, 13 deletions
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 9608358..90f2545 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -153,18 +153,15 @@ static inline uint16_t vring_get_used_event(VirtQueue *vq) return vring_avail_ring(vq, vq->vring.num); } -static inline void vring_used_ring_id(VirtQueue *vq, int i, uint32_t val) +static inline void vring_used_write(VirtQueue *vq, VRingUsedElem *uelem, + int i) { hwaddr pa; - pa = vq->vring.used + offsetof(VRingUsed, ring[i].id); - virtio_stl_phys(vq->vdev, pa, val); -} - -static inline void vring_used_ring_len(VirtQueue *vq, int i, uint32_t val) -{ - hwaddr pa; - pa = vq->vring.used + offsetof(VRingUsed, ring[i].len); - virtio_stl_phys(vq->vdev, pa, val); + virtio_tswap32s(vq->vdev, &uelem->id); + virtio_tswap32s(vq->vdev, &uelem->len); + pa = vq->vring.used + offsetof(VRingUsed, ring[i]); + address_space_write(&address_space_memory, pa, MEMTXATTRS_UNSPECIFIED, + (void *)uelem, sizeof(VRingUsedElem)); } static uint16_t vring_used_idx(VirtQueue *vq) @@ -273,15 +270,17 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len, unsigned int idx) { + VRingUsedElem uelem; + trace_virtqueue_fill(vq, elem, len, idx); virtqueue_unmap_sg(vq, elem, len); idx = (idx + vq->used_idx) % vq->vring.num; - /* Get a pointer to the next entry in the used ring. */ - vring_used_ring_id(vq, idx, elem->index); - vring_used_ring_len(vq, idx, len); + uelem.id = elem->index; + uelem.len = len; + vring_used_write(vq, &uelem, idx); } void virtqueue_flush(VirtQueue *vq, unsigned int count) |