Re: [PATCH 33/40] vdpa: batch multiple dma_unmap to a single call for vm stop

[Eugenio Perez Martin]

On Thu, Dec 7, 2023 at 7:51 PM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>
> Should help live migration downtime on source host. Below are the
> coalesced dma_unmap time series on 2 queue pair config (no
> dedicated descriptor group ASID for SVQ).
>
> 109531@1693367276.853503:vhost_vdpa_reset_device dev: 0x55c933926890
> 109531@1693367276.853513:vhost_vdpa_add_status dev: 0x55c933926890 status: 0x3
> 109531@1693367276.853520:vhost_vdpa_flush_map dev: 0x55c933926890 doit: 1 
> svq_flush: 0 persist: 1
> 109531@1693367276.853524:vhost_vdpa_set_config_call dev: 0x55c933926890 fd: -1
> 109531@1693367276.853579:vhost_vdpa_iotlb_begin_batch vdpa:0x7fa2aa895190 fd: 
> 16 msg_type: 2 type: 5
> 109531@1693367276.853586:vhost_vdpa_dma_unmap vdpa:0x7fa2aa895190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x1000 size: 0x2000 type: 3
> 109531@1693367276.853600:vhost_vdpa_dma_unmap vdpa:0x7fa2aa895190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x3000 size: 0x1000 type: 3
> 109531@1693367276.853618:vhost_vdpa_dma_unmap vdpa:0x7fa2aa895190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x4000 size: 0x2000 type: 3
> 109531@1693367276.853625:vhost_vdpa_dma_unmap vdpa:0x7fa2aa895190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x6000 size: 0x1000 type: 3
> 109531@1693367276.853630:vhost_vdpa_dma_unmap vdpa:0x7fa2aa84c190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x7000 size: 0x2000 type: 3
> 109531@1693367276.853636:vhost_vdpa_dma_unmap vdpa:0x7fa2aa84c190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x9000 size: 0x1000 type: 3
> 109531@1693367276.853642:vhost_vdpa_dma_unmap vdpa:0x7fa2aa84c190 fd: 16 
> msg_type: 2 asid: 0 iova: 0xa000 size: 0x2000 type: 3
> 109531@1693367276.853648:vhost_vdpa_dma_unmap vdpa:0x7fa2aa84c190 fd: 16 
> msg_type: 2 asid: 0 iova: 0xc000 size: 0x1000 type: 3
> 109531@1693367276.853654:vhost_vdpa_dma_unmap vdpa:0x7fa2aa6b6190 fd: 16 
> msg_type: 2 asid: 0 iova: 0xf000 size: 0x1000 type: 3
> 109531@1693367276.853660:vhost_vdpa_dma_unmap vdpa:0x7fa2aa6b6190 fd: 16 
> msg_type: 2 asid: 0 iova: 0x10000 size: 0x1000 type: 3
> 109531@1693367276.853666:vhost_vdpa_dma_unmap vdpa:0x7fa2aa6b6190 fd: 16 
> msg_type: 2 asid: 0 iova: 0xd000 size: 0x1000 type: 3
> 109531@1693367276.853670:vhost_vdpa_dma_unmap vdpa:0x7fa2aa6b6190 fd: 16 
> msg_type: 2 asid: 0 iova: 0xe000 size: 0x1000 type: 3
> 109531@1693367276.853675:vhost_vdpa_iotlb_end_batch vdpa:0x7fa2aa895190 fd: 
> 16 msg_type: 2 type: 6
> 109531@1693367277.014697:vhost_vdpa_get_vq_index dev: 0x55c933925de0 idx: 0 
> vq idx: 0
> 109531@1693367277.014747:vhost_vdpa_get_vq_index dev: 0x55c933925de0 idx: 1 
> vq idx: 1
> 109531@1693367277.014753:vhost_vdpa_get_vq_index dev: 0x55c9339262e0 idx: 2 
> vq idx: 2
> 109531@1693367277.014756:vhost_vdpa_get_vq_index dev: 0x55c9339262e0 idx: 3 
> vq idx: 3
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
>  hw/virtio/vhost-vdpa.c         |   7 +--
>  include/hw/virtio/vhost-vdpa.h |   3 ++
>  net/vhost-vdpa.c               | 112 
> +++++++++++++++++++++++++++--------------
>  3 files changed, 80 insertions(+), 42 deletions(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index d98704a..4010fd9 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -1162,8 +1162,8 @@ static void vhost_vdpa_svq_unmap_ring(struct vhost_vdpa 
> *v, hwaddr addr)
>      vhost_iova_tree_remove(v->shared->iova_tree, *result);
>  }
>
> -static void vhost_vdpa_svq_unmap_rings(struct vhost_dev *dev,
> -                                       const VhostShadowVirtqueue *svq)
> +void vhost_vdpa_svq_unmap_rings(struct vhost_dev *dev,
> +                                const VhostShadowVirtqueue *svq)
>  {
>      struct vhost_vdpa *v = dev->opaque;
>      struct vhost_vring_addr svq_addr;
> @@ -1346,17 +1346,14 @@ static void vhost_vdpa_svqs_stop(struct vhost_dev 
> *dev)
>          return;
>      }
>
> -    vhost_vdpa_dma_batch_begin_once(v->shared, v->address_space_id);
>      for (unsigned i = 0; i < v->shadow_vqs->len; ++i) {
>          VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, i);
>
>          vhost_svq_stop(svq);
> -        vhost_vdpa_svq_unmap_rings(dev, svq);
>
>          event_notifier_cleanup(&svq->hdev_kick);
>          event_notifier_cleanup(&svq->hdev_call);
>      }
> -    vhost_vdpa_dma_batch_end_once(v->shared, v->address_space_id);
>  }
>
>  static void vhost_vdpa_suspend(struct vhost_dev *dev)
> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> index aa13679..f426e2c 100644
> --- a/include/hw/virtio/vhost-vdpa.h
> +++ b/include/hw/virtio/vhost-vdpa.h
> @@ -112,6 +112,9 @@ int vhost_vdpa_dma_batch_end_once(VhostVDPAShared *s, 
> uint32_t asid);
>  int vhost_vdpa_load_setup(VhostVDPAShared *s, AddressSpace *dma_as);
>  int vhost_vdpa_load_cleanup(VhostVDPAShared *s, bool vhost_will_start);
>
> +void vhost_vdpa_svq_unmap_rings(struct vhost_dev *dev,
> +                                const VhostShadowVirtqueue *svq);
> +
>  typedef struct vdpa_iommu {
>      VhostVDPAShared *dev_shared;
>      IOMMUMemoryRegion *iommu_mr;
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 683619f..41714d1 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -29,6 +29,7 @@
>  #include "migration/migration.h"
>  #include "migration/misc.h"
>  #include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-vdpa.h"
>
>  /* Todo:need to add the multiqueue support here */
>  typedef struct VhostVDPAState {
> @@ -467,15 +468,89 @@ static int vhost_vdpa_net_data_load(NetClientState *nc)
>      return 0;
>  }
>
> +static void vhost_vdpa_cvq_unmap_buf(struct vhost_vdpa *v, void *addr)
> +{
> +    VhostIOVATree *tree = v->shared->iova_tree;
> +    DMAMap needle = {
> +        /*
> +         * No need to specify size or to look for more translations since
> +         * this contiguous chunk was allocated by us.
> +         */
> +        .translated_addr = (hwaddr)(uintptr_t)addr,
> +    };
> +    const DMAMap *map = vhost_iova_tree_find_iova(tree, &needle);
> +    int r;
> +
> +    if (unlikely(!map)) {
> +        error_report("Cannot locate expected map");
> +        return;
> +    }
> +
> +    r = vhost_vdpa_dma_unmap(v->shared, v->address_space_id, map->iova,
> +                             map->size + 1);
> +    if (unlikely(r != 0)) {
> +        error_report("Device cannot unmap: %s(%d)", g_strerror(r), r);
> +    }
> +
> +    vhost_iova_tree_remove(tree, *map);
> +}
> +
>  static void vhost_vdpa_net_client_stop(NetClientState *nc)
>  {
>      VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> +    struct vhost_vdpa *v = &s->vhost_vdpa;
> +    struct vhost_vdpa *last_vi = NULL;
> +    bool has_cvq = v->dev->vq_index_end % 2;
> +    int nvqp;
>
>      assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>
>      if (s->vhost_vdpa.index == 0) {
>          migration_remove_notifier(&s->migration_state);
>      }
> +
> +    if (v->dev->vq_index + v->dev->nvqs != v->dev->vq_index_end) {
> +        return;
> +    }
> +
> +    nvqp = (v->dev->vq_index_end + 1) / 2;
> +    for (int i = 0; i < nvqp; ++i) {
> +        VhostVDPAState *s_i = vhost_vdpa_net_get_nc_vdpa(s, i);
> +        struct vhost_vdpa *v_i = &s_i->vhost_vdpa;
> +
> +        if (!v_i->shadow_vqs_enabled) {
> +            continue;
> +        }
> +        if (!last_vi) {
> +            vhost_vdpa_dma_batch_begin_once(v_i->shared,
> +                                            v_i->address_space_id);
> +            last_vi = v_i;
> +        } else if (last_vi->address_space_id != v_i->address_space_id) {
> +            vhost_vdpa_dma_batch_end_once(last_vi->shared,
> +                                          last_vi->address_space_id);
> +            vhost_vdpa_dma_batch_begin_once(v_i->shared,
> +                                            v_i->address_space_id);
> +            last_vi = v_i;
> +        }
> +
> +        for (unsigned j = 0; j < v_i->shadow_vqs->len; ++j) {
> +            VhostShadowVirtqueue *svq = g_ptr_array_index(v_i->shadow_vqs, 
> j);
> +
> +            vhost_vdpa_svq_unmap_rings(v_i->dev, svq);
> +        }
> +    }
> +    if (has_cvq) {
> +        if (last_vi) {
> +            assert(last_vi->address_space_id == v->address_space_id);
> +        }
> +        vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
> +        vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
> +    }
> +    if (last_vi) {
> +        vhost_vdpa_dma_batch_end_once(last_vi->shared,
> +                                      last_vi->address_space_id);
> +        last_vi = NULL;
> +    }

Since we've delayed the guest unmap memory to _cleanup, why not delay
these unmaps to cleanup too?

>  }
>
>  static int vhost_vdpa_net_load_setup(NetClientState *nc, NICState *nic)
> @@ -585,33 +660,6 @@ static int64_t vhost_vdpa_get_vring_desc_group(int 
> device_fd,
>      return state.num;
>  }
>
> -static void vhost_vdpa_cvq_unmap_buf(struct vhost_vdpa *v, void *addr)
> -{
> -    VhostIOVATree *tree = v->shared->iova_tree;
> -    DMAMap needle = {
> -        /*
> -         * No need to specify size or to look for more translations since
> -         * this contiguous chunk was allocated by us.
> -         */
> -        .translated_addr = (hwaddr)(uintptr_t)addr,
> -    };
> -    const DMAMap *map = vhost_iova_tree_find_iova(tree, &needle);
> -    int r;
> -
> -    if (unlikely(!map)) {
> -        error_report("Cannot locate expected map");
> -        return;
> -    }
> -
> -    r = vhost_vdpa_dma_unmap(v->shared, v->address_space_id, map->iova,
> -                             map->size + 1);
> -    if (unlikely(r != 0)) {
> -        error_report("Device cannot unmap: %s(%d)", g_strerror(r), r);
> -    }
> -
> -    vhost_iova_tree_remove(tree, *map);
> -}
> -
>  /** Map CVQ buffer. */
>  static int vhost_vdpa_cvq_map_buf(struct vhost_vdpa *v, void *buf, size_t 
> size,
>                                    bool write)
> @@ -740,18 +788,8 @@ err:
>
>  static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
>  {
> -    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> -    struct vhost_vdpa *v = &s->vhost_vdpa;
> -
>      assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>
> -    if (s->vhost_vdpa.shadow_vqs_enabled) {
> -        vhost_vdpa_dma_batch_begin_once(v->shared, v->address_space_id);
> -        vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
> -        vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
> -        vhost_vdpa_dma_batch_end_once(v->shared, v->address_space_id);
> -    }
> -
>      vhost_vdpa_net_client_stop(nc);
>  }
>
> --
> 1.8.3.1
>