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

[Eugenio Perez Martin]

On Tue, Nov 15, 2022 at 4:04 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Tue, Nov 15, 2022 at 12:31 AM Eugenio Perez Martin
> <eperezma@redhat.com> wrote:
> >
> > On Mon, Nov 14, 2022 at 5:30 AM Jason Wang <jasowang@redhat.com> wrote:
> > >
> > >
> > > 在 2022/11/11 21:12, Eugenio Perez Martin 写道:
> > > > 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?
> > >
> > >
> > > I think "iova_tree" is something that is internal to svq implementation,
> > > it's better to define the name from the view of vhost_vdpa level.
> > >
> >
> > I don't get this, vhost_vdpa struct already has a pointer to its iova_tree.
>
> Yes, this is a suggestion to improve the readability of the code. So
> what I meant is to have a name to demonstrate why we need to use
> iova_tree instead of "uses_iova_tree".
>

I understand.

Knowing that the listener will be always bound to data vqs (being net,
blk, ...), I think it is ok to rename it to shadow_data.

But I think there is no way to add shadow_cvq properly from
hw/virtio/vhost-vdpa.c , since we don't know if the vhost_vdpa belongs
to a datapath or not. Would it work just to rename listener_shadow_vq
to shadow_data?

Thanks!