From e6db5df7e2c6e64846f47a6785a9a67f08574790 Mon Sep 17 00:00:00 2001 From: Eugenio Pérez Date: Thu, 12 Aug 2021 16:09:33 +0200 Subject: vhost-vdpa: Do not send empty IOTLB update batches With the introduction of the batch hinting, meaningless batches can be created with no IOTLB updates if the memory region was skipped by vhost_vdpa_listener_skipped_section. This is the case of host notifiers memory regions, device un/realize, and others. This causes the vdpa device to receive dma mapping settings with no changes, a possibly expensive operation for nothing. To avoid that, VHOST_IOTLB_BATCH_BEGIN hint is delayed until we have a meaningful (not skipped section) mapping or unmapping operation, and VHOST_IOTLB_BATCH_END is not written unless at least one of _UPDATE / _INVALIDATE has been issued. v3: * Use a bool instead of a counter avoiding potential number wrapping * Fix bad check on _commit * Move VHOST_BACKEND_F_IOTLB_BATCH check to vhost_vdpa_iotlb_batch_begin_once v2 (from RFC): * Rename misleading name * Abstract start batching function for listener_add/del Signed-off-by: Eugenio Pérez Message-Id: <20210812140933.226288-1-eperezma@redhat.com> Acked-by: Jason Wang Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- include/hw/virtio/vhost-vdpa.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h index 9188226d8b..a8963da2d9 100644 --- a/include/hw/virtio/vhost-vdpa.h +++ b/include/hw/virtio/vhost-vdpa.h @@ -22,6 +22,7 @@ typedef struct VhostVDPAHostNotifier { typedef struct vhost_vdpa { int device_fd; uint32_t msg_type; + bool iotlb_batch_begin_sent; MemoryListener listener; struct vhost_dev *dev; VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX]; -- cgit v1.2.3-55-g7522