On Fri, Dec 8, 2023 at 2:50 AM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>
> Today memory listener is unregistered in vhost_vdpa_reset_status
> unconditionally, due to which all the maps will be flushed away
> from the iotlb. However, map flush is not always needed, and
> doing it from performance hot path may have innegligible latency
> impact that affects VM reboot time or brown out period during
> live migration.
>
> Leverage the IOTLB_PERSIST backend featuae, which ensures durable
> iotlb maps and not disappearing even across reset. When it is
> supported, we may conditionally keep the maps for cases where the
> guest memory mapping doesn't change. Prepare a function so that
> the next patch will be able to use it to keep the maps.
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
> hw/virtio/trace-events | 1 +
> hw/virtio/vhost-vdpa.c | 20 ++++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 77905d1..9725d44 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -66,6 +66,7 @@ vhost_vdpa_set_owner(void *dev) "dev: %p"
> vhost_vdpa_vq_get_addr(void *dev, void *vq, uint64_t desc_user_addr, uint64_t avail_user_addr, uint64_t used_user_addr) "dev: %p vq: %p desc_user_addr: 0x%"PRIx64" avail_user_addr: 0x%"PRIx64" used_user_addr: 0x%"PRIx64
> vhost_vdpa_get_iova_range(void *dev, uint64_t first, uint64_t last) "dev: %p first: 0x%"PRIx64" last: 0x%"PRIx64
> vhost_vdpa_set_config_call(void *dev, int fd)"dev: %p fd: %d"
> +vhost_vdpa_maybe_flush_map(void *dev, bool reg, bool flush, bool persist) "dev: %p registered: %d flush_map: %d iotlb_persistent: %d"
>
> # virtio.c
> virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned out_num) "elem %p size %zd in_num %u out_num %u"
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index ea2dfc8..31e0a55 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -1471,6 +1471,26 @@ out_stop:
> return ok ? 0 : -1;
> }
>
> +static void vhost_vdpa_maybe_flush_map(struct vhost_dev *dev)
Nit: Not a native speaker, but it looks like
vhost_vdpa_may_flush_map() is better.
> +{
> + struct vhost_vdpa *v = dev->opaque;
> +
> + trace_vhost_vdpa_maybe_flush_map(dev, v->shared->listener_registered,
> + v->shared->flush_map,
> + !!(dev->backend_cap &
> + BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST)));
> +
> + if (!v->shared->listener_registered) {
> + return;
> + }
> +
> + if (!(dev->backend_cap & BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST)) ||
> + v->shared->flush_map) {
> + memory_listener_unregister(&v->shared->listener);
> + v->shared->listener_registered = false;
> + }
Others look good.
Thanks
> +}
> +
> static void vhost_vdpa_reset_status(struct vhost_dev *dev)
> {
> struct vhost_vdpa *v = dev->opaque;
> --
> 1.8.3.1
>