From e6db5df7e2c6e64846f47a6785a9a67f08574790 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= Date: Thu, 12 Aug 2021 16:09:33 +0200 Subject: [PATCH] vhost-vdpa: Do not send empty IOTLB update batches MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- hw/virtio/vhost-vdpa.c | 35 ++++++++++++++++++++++------------ include/hw/virtio/vhost-vdpa.h | 1 + 2 files changed, 24 insertions(+), 12 deletions(-) diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c index 4fa414feea..ca1227e5dc 100644 --- a/hw/virtio/vhost-vdpa.c +++ b/hw/virtio/vhost-vdpa.c @@ -89,19 +89,13 @@ static int vhost_vdpa_dma_unmap(struct vhost_vdpa *v, hwaddr iova, return ret; } -static void vhost_vdpa_listener_begin(MemoryListener *listener) +static void vhost_vdpa_listener_begin_batch(struct vhost_vdpa *v) { - struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener); - struct vhost_dev *dev = v->dev; - struct vhost_msg_v2 msg = {}; int fd = v->device_fd; - - if (!(dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH))) { - return; - } - - msg.type = v->msg_type; - msg.iotlb.type = VHOST_IOTLB_BATCH_BEGIN; + struct vhost_msg_v2 msg = { + .type = v->msg_type, + .iotlb.type = VHOST_IOTLB_BATCH_BEGIN, + }; if (write(fd, &msg, sizeof(msg)) != sizeof(msg)) { error_report("failed to write, fd=%d, errno=%d (%s)", @@ -109,6 +103,16 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener) } } +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v) +{ + if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH) && + !v->iotlb_batch_begin_sent) { + vhost_vdpa_listener_begin_batch(v); + } + + v->iotlb_batch_begin_sent = true; +} + static void vhost_vdpa_listener_commit(MemoryListener *listener) { struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener); @@ -120,6 +124,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener) return; } + if (!v->iotlb_batch_begin_sent) { + return; + } + msg.type = v->msg_type; msg.iotlb.type = VHOST_IOTLB_BATCH_END; @@ -127,6 +135,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener) error_report("failed to write, fd=%d, errno=%d (%s)", fd, errno, strerror(errno)); } + + v->iotlb_batch_begin_sent = false; } static void vhost_vdpa_listener_region_add(MemoryListener *listener, @@ -170,6 +180,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener, llsize = int128_sub(llend, int128_make64(iova)); + vhost_vdpa_iotlb_batch_begin_once(v); ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize), vaddr, section->readonly); if (ret) { @@ -221,6 +232,7 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener, llsize = int128_sub(llend, int128_make64(iova)); + vhost_vdpa_iotlb_batch_begin_once(v); ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize)); if (ret) { error_report("vhost_vdpa dma unmap error!"); @@ -234,7 +246,6 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener, * depends on the addnop(). */ static const MemoryListener vhost_vdpa_memory_listener = { - .begin = vhost_vdpa_listener_begin, .commit = vhost_vdpa_listener_commit, .region_add = vhost_vdpa_listener_region_add, .region_del = vhost_vdpa_listener_region_del, 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];