Next patches will register the vhost_vdpa memory listener while the VM
is migrating at the destination, so we can map the memory to the device
before stopping the VM at the source.  The main goal is to reduce the
downtime.

However, the destination QEMU is unaware of which vhost_vdpa device will
register its memory_listener.  If the source guest has CVQ enabled, it
will be the CVQ device.  Otherwise, it  will be the first one.

Move the shadow_data member to VhostVDPAShared so all vhost_vdpa can use
it, rather than always in the first or last vhost_vdpa.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v1 from RFC:
* Fix vhost_vdpa_net_cvq_start checking for always_svq instead of
  shadow_data.  This could cause CVQ not being shadowed if
  vhost_vdpa_net_cvq_start was called in the middle of a migration.
---
 include/hw/virtio/vhost-vdpa.h |  5 +++--
 hw/virtio/vhost-vdpa.c         |  6 +++---
 net/vhost-vdpa.c               | 23 ++++++-----------------
 3 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 8d52a7e498..01e0f25e27 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -36,6 +36,9 @@ typedef struct vhost_vdpa_shared {
 
     /* IOVA mapping used by the Shadow Virtqueue */
     VhostIOVATree *iova_tree;
+
+    /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
+    bool shadow_data;
 } VhostVDPAShared;
 
 typedef struct vhost_vdpa {
@@ -47,8 +50,6 @@ typedef struct vhost_vdpa {
     MemoryListener listener;
     uint64_t acked_features;
     bool shadow_vqs_enabled;
-    /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
-    bool shadow_data;
     /* Device suspended successfully */
     bool suspended;
     VhostVDPAShared *shared;
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 2bceadd118..ec028e4c56 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -353,7 +353,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
                                          vaddr, section->readonly);
 
     llsize = int128_sub(llend, int128_make64(iova));
-    if (v->shadow_data) {
+    if (v->shared->shadow_data) {
         int r;
 
         mem_region.translated_addr = (hwaddr)(uintptr_t)vaddr,
@@ -380,7 +380,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
     return;
 
 fail_map:
-    if (v->shadow_data) {
+    if (v->shared->shadow_data) {
         vhost_iova_tree_remove(v->shared->iova_tree, mem_region);
     }
 
@@ -435,7 +435,7 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
 
     llsize = int128_sub(llend, int128_make64(iova));
 
-    if (v->shadow_data) {
+    if (v->shared->shadow_data) {
         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 7be2c30ad3..2376d9989a 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -290,15 +290,6 @@ static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
     return size;
 }
 
-/** From any vdpa net client, get the netclient of the first queue pair */
-static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
-{
-    NICState *nic = qemu_get_nic(s->nc.peer);
-    NetClientState *nc0 = qemu_get_peer(nic->ncs, 0);
-
-    return DO_UPCAST(VhostVDPAState, nc, nc0);
-}
-
 static void vhost_vdpa_net_log_global_enable(VhostVDPAState *s, bool enable)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
@@ -369,10 +360,10 @@ static int vhost_vdpa_net_data_start(NetClientState *nc)
     if (s->always_svq ||
         migration_is_setup_or_active(migrate_get_current()->state)) {
         v->shadow_vqs_enabled = true;
-        v->shadow_data = true;
+        v->shared->shadow_data = true;
     } else {
         v->shadow_vqs_enabled = false;
-        v->shadow_data = false;
+        v->shared->shadow_data = false;
     }
 
     if (v->index == 0) {
@@ -523,7 +514,7 @@ dma_map_err:
 
 static int vhost_vdpa_net_cvq_start(NetClientState *nc)
 {
-    VhostVDPAState *s, *s0;
+    VhostVDPAState *s;
     struct vhost_vdpa *v;
     int64_t cvq_group;
     int r;
@@ -534,12 +525,10 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
     s = DO_UPCAST(VhostVDPAState, nc, nc);
     v = &s->vhost_vdpa;
 
-    s0 = vhost_vdpa_net_first_nc_vdpa(s);
-    v->shadow_data = s0->vhost_vdpa.shadow_vqs_enabled;
-    v->shadow_vqs_enabled = s0->vhost_vdpa.shadow_vqs_enabled;
+    v->shadow_vqs_enabled = v->shared->shadow_data;
     s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
 
-    if (s->vhost_vdpa.shadow_data) {
+    if (v->shared->shadow_data) {
         /* SVQ is already configured for all virtqueues */
         goto out;
     }
@@ -1688,12 +1677,12 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->always_svq = svq;
     s->migration_state.notify = NULL;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
-    s->vhost_vdpa.shadow_data = svq;
     if (queue_pair_index == 0) {
         vhost_vdpa_net_valid_svq_features(features,
                                           &s->vhost_vdpa.migration_blocker);
         s->vhost_vdpa.shared = g_new0(VhostVDPAShared, 1);
         s->vhost_vdpa.shared->iova_range = iova_range;
+        s->vhost_vdpa.shared->shadow_data = svq;
     } else if (!is_datapath) {
         s->cvq_cmd_out_buffer = mmap(NULL, vhost_vdpa_net_cvq_cmd_page_len(),
                                      PROT_READ | PROT_WRITE,
-- 
2.39.3

On 11/24/2023 9:14 AM, Eugenio Pérez wrote:
> Next patches will register the vhost_vdpa memory listener while the VM
> is migrating at the destination, so we can map the memory to the device
> before stopping the VM at the source.  The main goal is to reduce the
> downtime.
>
> However, the destination QEMU is unaware of which vhost_vdpa device will
> register its memory_listener.  If the source guest has CVQ enabled, it
> will be the CVQ device.  Otherwise, it  will be the first one.
>
> Move the shadow_data member to VhostVDPAShared so all vhost_vdpa can use
> it, rather than always in the first or last vhost_vdpa.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
> v1 from RFC:
> * Fix vhost_vdpa_net_cvq_start checking for always_svq instead of
>    shadow_data.  This could cause CVQ not being shadowed if
>    vhost_vdpa_net_cvq_start was called in the middle of a migration.
> ---
>   include/hw/virtio/vhost-vdpa.h |  5 +++--
>   hw/virtio/vhost-vdpa.c         |  6 +++---
>   net/vhost-vdpa.c               | 23 ++++++-----------------
>   3 files changed, 12 insertions(+), 22 deletions(-)
>
> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> index 8d52a7e498..01e0f25e27 100644
> --- a/include/hw/virtio/vhost-vdpa.h
> +++ b/include/hw/virtio/vhost-vdpa.h
> @@ -36,6 +36,9 @@ typedef struct vhost_vdpa_shared {
>   
>       /* IOVA mapping used by the Shadow Virtqueue */
>       VhostIOVATree *iova_tree;
> +
> +    /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
> +    bool shadow_data;
>   } VhostVDPAShared;
>   
>   typedef struct vhost_vdpa {
> @@ -47,8 +50,6 @@ typedef struct vhost_vdpa {
>       MemoryListener listener;
>       uint64_t acked_features;
>       bool shadow_vqs_enabled;
> -    /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
> -    bool shadow_data;
>       /* Device suspended successfully */
>       bool suspended;
>       VhostVDPAShared *shared;
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 2bceadd118..ec028e4c56 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -353,7 +353,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
>                                            vaddr, section->readonly);
>   
>       llsize = int128_sub(llend, int128_make64(iova));
> -    if (v->shadow_data) {
> +    if (v->shared->shadow_data) {
>           int r;
>   
>           mem_region.translated_addr = (hwaddr)(uintptr_t)vaddr,
> @@ -380,7 +380,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
>       return;
>   
>   fail_map:
> -    if (v->shadow_data) {
> +    if (v->shared->shadow_data) {
>           vhost_iova_tree_remove(v->shared->iova_tree, mem_region);
>       }
>   
> @@ -435,7 +435,7 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
>   
>       llsize = int128_sub(llend, int128_make64(iova));
>   
> -    if (v->shadow_data) {
> +    if (v->shared->shadow_data) {
>           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 7be2c30ad3..2376d9989a 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -290,15 +290,6 @@ static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
>       return size;
>   }
>   
> -/** From any vdpa net client, get the netclient of the first queue pair */
> -static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
> -{
> -    NICState *nic = qemu_get_nic(s->nc.peer);
> -    NetClientState *nc0 = qemu_get_peer(nic->ncs, 0);
> -
> -    return DO_UPCAST(VhostVDPAState, nc, nc0);
> -}
> -
Fine with the removal as the only caller is gone. However, in my series 
I will resurrect this function for fields that are not shared and vq 
specific. Not sure there's sort of way not failing the build while 
keeping unused function around.

>   static void vhost_vdpa_net_log_global_enable(VhostVDPAState *s, bool enable)
>   {
>       struct vhost_vdpa *v = &s->vhost_vdpa;
> @@ -369,10 +360,10 @@ static int vhost_vdpa_net_data_start(NetClientState *nc)
>       if (s->always_svq ||
>           migration_is_setup_or_active(migrate_get_current()->state)) {
>           v->shadow_vqs_enabled = true;
> -        v->shadow_data = true;
> +        v->shared->shadow_data = true;
Noted this shared shadow_data needs to be set only once. I will also 
change this in my series. No actual code change is requested.

>       } else {
>           v->shadow_vqs_enabled = false;
> -        v->shadow_data = false;
> +        v->shared->shadow_data = false;
>       }
>   
>       if (v->index == 0) {
> @@ -523,7 +514,7 @@ dma_map_err:
>   
>   static int vhost_vdpa_net_cvq_start(NetClientState *nc)
>   {
> -    VhostVDPAState *s, *s0;
> +    VhostVDPAState *s;
>       struct vhost_vdpa *v;
>       int64_t cvq_group;
>       int r;
> @@ -534,12 +525,10 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
>       s = DO_UPCAST(VhostVDPAState, nc, nc);
>       v = &s->vhost_vdpa;
>   
> -    s0 = vhost_vdpa_net_first_nc_vdpa(s);
> -    v->shadow_data = s0->vhost_vdpa.shadow_vqs_enabled;
> -    v->shadow_vqs_enabled = s0->vhost_vdpa.shadow_vqs_enabled;
> +    v->shadow_vqs_enabled = v->shared->shadow_data;
This new code looks fine.

Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>

>       s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
>   
> -    if (s->vhost_vdpa.shadow_data) {
> +    if (v->shared->shadow_data) {
>           /* SVQ is already configured for all virtqueues */
>           goto out;
>       }
> @@ -1688,12 +1677,12 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
>       s->always_svq = svq;
>       s->migration_state.notify = NULL;
>       s->vhost_vdpa.shadow_vqs_enabled = svq;
> -    s->vhost_vdpa.shadow_data = svq;
>       if (queue_pair_index == 0) {
>           vhost_vdpa_net_valid_svq_features(features,
>                                             &s->vhost_vdpa.migration_blocker);
>           s->vhost_vdpa.shared = g_new0(VhostVDPAShared, 1);
>           s->vhost_vdpa.shared->iova_range = iova_range;
> +        s->vhost_vdpa.shared->shadow_data = svq;
>       } else if (!is_datapath) {
>           s->cvq_cmd_out_buffer = mmap(NULL, vhost_vdpa_net_cvq_cmd_page_len(),
>                                        PROT_READ | PROT_WRITE,