From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53092) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aS8IB-0001gk-1M for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aS8IA-0002F3-5B for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35211) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aS8I9-0002Ez-Vc for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:10 -0500 Date: Sat, 6 Feb 2016 21:13:06 +0200 From: "Michael S. Tsirkin" Message-ID: <1454784308-21177-15-git-send-email-mst@redhat.com> References: <1454784308-21177-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1454784308-21177-1-git-send-email-mst@redhat.com> Subject: [Qemu-devel] [PULL v2 14/45] virtio: combine write of an entry into used ring List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Cornelia Huck , Peter Maydell , Eduardo Habkost , Vincenzo Maffione , Paolo Bonzini From: Vincenzo Maffione 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 Message-Id: Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/virtio/virtio.c | 25 ++++++++++++------------- 1 file 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) -- MST