Re: [PATCH v6 09/10] vdpa: Add listener_shadow_vq to vhost_vdpa

[Eugenio Perez Martin <eperezma@redhat.com>]

On Fri, Nov 11, 2022 at 8:49 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2022/11/10 21:47, Eugenio Perez Martin 写道:
> > On Thu, Nov 10, 2022 at 7:01 AM Jason Wang <jasowang@redhat.com> wrote:
> >> On Wed, Nov 9, 2022 at 1:08 AM Eugenio Pérez <eperezma@redhat.com> wrote:
> >>> The memory listener that thells the device how to convert GPA to qemu's
> >>> va is registered against CVQ vhost_vdpa. This series try to map the
> >>> memory listener translations to ASID 0, while it maps the CVQ ones to
> >>> ASID 1.
> >>>
> >>> Let's tell the listener if it needs to register them on iova tree or
> >>> not.
> >>>
> >>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> >>> ---
> >>> v5: Solve conflict about vhost_iova_tree_remove accepting mem_region by
> >>>      value.
> >>> ---
> >>>   include/hw/virtio/vhost-vdpa.h | 2 ++
> >>>   hw/virtio/vhost-vdpa.c         | 6 +++---
> >>>   net/vhost-vdpa.c               | 1 +
> >>>   3 files changed, 6 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> >>> index 6560bb9d78..0c3ed2d69b 100644
> >>> --- a/include/hw/virtio/vhost-vdpa.h
> >>> +++ b/include/hw/virtio/vhost-vdpa.h
> >>> @@ -34,6 +34,8 @@ typedef struct vhost_vdpa {
> >>>       struct vhost_vdpa_iova_range iova_range;
> >>>       uint64_t acked_features;
> >>>       bool shadow_vqs_enabled;
> >>> +    /* The listener must send iova tree addresses, not GPA */
>
>
> Btw, cindy's vIOMMU series will make it not necessarily GPA any more.
>

Yes, this comment should be tuned then. But the SVQ iova_tree will not
be equal to vIOMMU one because shadow vrings.

But maybe SVQ can inspect both instead of having all the duplicated entries.

>
> >>> +    bool listener_shadow_vq;
> >>>       /* IOVA mapping used by the Shadow Virtqueue */
> >>>       VhostIOVATree *iova_tree;
> >>>       GPtrArray *shadow_vqs;
> >>> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> >>> index 8fd32ba32b..e3914fa40e 100644
> >>> --- a/hw/virtio/vhost-vdpa.c
> >>> +++ b/hw/virtio/vhost-vdpa.c
> >>> @@ -220,7 +220,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> >>>                                            vaddr, section->readonly);
> >>>
> >>>       llsize = int128_sub(llend, int128_make64(iova));
> >>> -    if (v->shadow_vqs_enabled) {
> >>> +    if (v->listener_shadow_vq) {
> >>>           int r;
> >>>
> >>>           mem_region.translated_addr = (hwaddr)(uintptr_t)vaddr,
> >>> @@ -247,7 +247,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> >>>       return;
> >>>
> >>>   fail_map:
> >>> -    if (v->shadow_vqs_enabled) {
> >>> +    if (v->listener_shadow_vq) {
> >>>           vhost_iova_tree_remove(v->iova_tree, mem_region);
> >>>       }
> >>>
> >>> @@ -292,7 +292,7 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
> >>>
> >>>       llsize = int128_sub(llend, int128_make64(iova));
> >>>
> >>> -    if (v->shadow_vqs_enabled) {
> >>> +    if (v->listener_shadow_vq) {
> >>>           const DMAMap *result;
> >>>           const void *vaddr = memory_region_get_ram_ptr(section->mr) +
> >>>               section->offset_within_region +
> >>> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> >>> index 85a318faca..02780ee37b 100644
> >>> --- a/net/vhost-vdpa.c
> >>> +++ b/net/vhost-vdpa.c
> >>> @@ -570,6 +570,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
> >>>       s->vhost_vdpa.index = queue_pair_index;
> >>>       s->always_svq = svq;
> >>>       s->vhost_vdpa.shadow_vqs_enabled = svq;
> >>> +    s->vhost_vdpa.listener_shadow_vq = svq;
> >> Any chance those above two can differ?
> >>
> > If CVQ is shadowed but data VQs are not, shadow_vqs_enabled is true
> > but listener_shadow_vq is not.
> >
> > It is more clear in the next commit, where only shadow_vqs_enabled is
> > set to true at vhost_vdpa_net_cvq_start.
>
>
> Ok, the name looks a little bit confusing. I wonder if it's better to
> use shadow_cvq and shadow_data ?
>

I'm ok with renaming it, but struct vhost_vdpa is generic across all
kind of devices, and it does not know if it is a datapath or not for
the moment.

Maybe listener_uses_iova_tree?

Thanks!