On Thu, Aug 12, 2021 at 12:32 AM Eugenio Pérez <epere...@redhat.com> wrote:
>
> 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.
>
> Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> ---
> include/hw/virtio/vhost-vdpa.h | 1 +
> hw/virtio/vhost-vdpa.c | 50 ++++++++++++++++++++++++++--------
> 2 files changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> index e98e327f12..6538572a6f 100644
> --- a/include/hw/virtio/vhost-vdpa.h
> +++ b/include/hw/virtio/vhost-vdpa.h
> @@ -23,6 +23,7 @@ typedef struct vhost_vdpa {
> int device_fd;
> int index;
> uint32_t msg_type;
> + size_t n_mr_updated;
> MemoryListener listener;
> struct vhost_dev *dev;
> VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 6ce94a1f4d..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener
> *listener)
> }
> }
>
> +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
> +{
> + return v->n_mr_updated != 0;
> +}
> +
> +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
> +{
> + if (!vhost_vdpa_iotlb_batch_is_started(v)) {
> + vhost_vdpa_listener_begin_batch(v);
> + }
> +
> + v->n_mr_updated++;
> +}
> +
> +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
> +{
> + v->n_mr_updated = 0;
> +}
> +
> static void vhost_vdpa_listener_commit(MemoryListener *listener)
> {
> struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa,
> listener);
> @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener
> *listener)
> return;
> }
>
> + if (vhost_vdpa_iotlb_batch_is_started(v)) {
> + return;
> + }
> +
> msg.type = v->msg_type;
> msg.iotlb.type = VHOST_IOTLB_BATCH_END;
>
> @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener
> *listener)
> error_report("failed to write, fd=%d, errno=%d (%s)",
> fd, errno, strerror(errno));
> }
> +
> + vhost_vdpa_iotlb_batch_reset(v);
> }
>
> static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> @@ -170,6 +189,10 @@ static void
> vhost_vdpa_listener_region_add(MemoryListener *listener,
>
> llsize = int128_sub(llend, int128_make64(iova));
>
> + if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
Let's move this in to vhost_vdpa_iotlb_batch_begin_once()?
> + vhost_vdpa_iotlb_batch_begin_once(v);
> + }
> +
> ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
> vaddr, section->readonly);
> if (ret) {
> @@ -221,6 +244,10 @@ static void
> vhost_vdpa_listener_region_del(MemoryListener *listener,
>
> llsize = int128_sub(llend, int128_make64(iova));
>
> + if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> + vhost_vdpa_iotlb_batch_begin_once(v);
> + }
> +
Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit?
Others look good.
Thanks
> ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
> if (ret) {
> error_report("vhost_vdpa dma unmap error!");
> @@ -234,7 +261,6 @@ 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,
> --
> 2.27.0
>
