Re: [PATCH v2 3/4] vdpa: show dev config as-is in "vdpa dev show" output

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On 10/20/2022 2:13 PM, Parav Pandit wrote:
From: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
Sent: Thursday, October 20, 2022 2:12 PM


On 10/19/2022 10:25 PM, Jason Wang wrote:
On Wed, Oct 19, 2022 at 8:56 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
wrote:
Live migration of vdpa would typically require re-instate vdpa device
with an idential set of configs on the destination node, same way as
how source node created the device in the first place. In order to
save orchestration software from memorizing and keeping track of vdpa
config, it will be helpful if the vdpa tool provides the aids for
exporting the initial configs from which vdpa device was created
as-is. The "vdpa dev show" command seems to be the right vehicle for
that. It is unlike the "vdpa dev config show" command output that
usually goes with the live value in the device config space, which is
not quite reliable subject to the dynamics of feature negotiation and
possible change in device config space.

Examples:

1) Create vDPA by default without any config attribute

$ vdpa dev add mgmtdev pci/0000:41:04.2 name vdpa0 $ vdpa dev show
vdpa0
vdpa0: type network mgmtdev pci/0000:41:04.2 vendor_id 5555 max_vqs
9
max_vq_size 256 $ vdpa dev -jp show vdpa0 {
     "dev": {
         "vdpa0": {
             "type": "network",
             "mgmtdev": "pci/0000:41:04.2",
             "vendor_id": 5555,
             "max_vqs": 9,
             "max_vq_size": 256,
         }
     }
}

2) Create vDPA with config attribute(s) specified

$ vdpa dev add mgmtdev pci/0000:41:04.2 name vdpa0 \
     mac e4:11:c6:d3:45:f0 max_vq_pairs 4 $ vdpa dev show
vdpa0: type network mgmtdev pci/0000:41:04.2 vendor_id 5555 max_vqs
9 max_vq_size 256
   virtio_config: mac e4:11:c6:d3:45:f0 max_vq_pairs 4 $ vdpa dev -jp
show {
     "dev": {
         "vdpa0": {
             "type": "network",
             "mgmtdev": "pci/0000:41:04.2",
             "vendor_id": 5555,
             "max_vqs": 9,
             "max_vq_size": 256,
             "virtio_config": {
Since most config is related to virtio.
May be better to do
s/virtio_config/static_config or
s/virto_config/dev_config

This clearly indicates that this was the device static configuration.
The name was suggested by Jason, and it seems he prefers naming with init/initial. How about change it to initial_config?


                 "mac": "e4:11:c6:d3:45:f0",
                 "max_vq_pairs": 4
             }
         }
     }
}

Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
---
  drivers/vdpa/vdpa.c | 39 +++++++++++++++++++++++++++++++++++++++
  1 file changed, 39 insertions(+)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index
566c1c6..91eca6d 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -677,6 +677,41 @@ static int vdpa_nl_cmd_dev_del_set_doit(struct
sk_buff *skb, struct genl_info *i
  }

  static int
+vdpa_dev_cfgattrs_fill(struct vdpa_device *vdev, struct sk_buff
+*msg, u32 device_id) {
+       struct vdpa_dev_set_config *cfg = &vdev->vdev_cfg;
+       int err = -EMSGSIZE;
+
+       if (!cfg->mask)
+               return 0;
+
+       switch (device_id) {
+       case VIRTIO_ID_NET:
+               if ((cfg->mask &
BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MACADDR)) != 0 &&
+                   nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR,
+                           sizeof(cfg->net.mac), cfg->net.mac))
+                       return err;
+               if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU)) !=
0 &&
+                   nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, cfg-
net.mtu))
+                       return err;
+               if ((cfg->mask &
BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP)) != 0 &&
+                   nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MAX_VQP,
+                               cfg->net.max_vq_pairs))
+                       return err;
+               break;
This makes me think if we can reuse the virtio_net_config structure
other than duplicate it slowly with a dedicated nested structure
inside vdpa_dev_set_config then we can reuse the
vdpa_dev_net_config_fill().
Adding Parav.

I think for now the struct vdpa_dev_set_config has just a few fields, so it's
not very obvious. But from what I understand, the vdpa_dev_set_config
struct is designed to be built around vdpa configurables, without getting it
limited by what's exposed by the virtio device config structure, such as
virtio_net_config. 
Sure. Vdpa_dev_set_config can expand for fields outside of virtio_net_config structure space, but it should be close to virtio spec definition like you described below or close to Linux kernel objects.
Yes. The fields in vdpa_dev_set_config should definitely be virtio related. Though I feel it may be too early to generalize with virtio config space structure like virtio_net_config. There are just 3 fields at the moment and network device only. It's hard to predicate how it may expand in future. Let the vdpa config struct out grow from virtio config struct for now. If it turns out too much duplication between the two, we can then consider consolidating at some future point. Any objection?

-Siwei


At present it can handle another 62 more fields, which I think is good enough for midterm.

For instance, there could be possibility for vdpa user to
specify the size of MAC unicast or multicast address table, which is not
defined anywhere in the virtio_net_config. I think it's important to match
such configuration (which may not even be defined in spec) for src&dst vdpa
devices involving the live migration.

-Siwei
Thanks

+       default:
+               break;
+       }
+
+       if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_FEATURES)) != 0 &&
+           nla_put_u64_64bit(msg, VDPA_ATTR_DEV_FEATURES,
+                             cfg->device_features, VDPA_ATTR_PAD))
+               return err;
+
+       return 0;
+}
+
+static int
  vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
u32 seq,
               int flags, struct netlink_ext_ack *extack)
  {
@@ -715,6 +750,10 @@ static int vdpa_nl_cmd_dev_del_set_doit(struct
sk_buff *skb, struct genl_info *i
         if (nla_put_u16(msg, VDPA_ATTR_DEV_MIN_VQ_SIZE, min_vq_size))
                 goto msg_err;

+       err = vdpa_dev_cfgattrs_fill(vdev, msg, device_id);
+       if (err)
+               goto msg_err;
+
         genlmsg_end(msg, hdr);
         return 0;

--
1.8.3.1


    

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