Re: [PATCH V2 2/3] vdpa_sim_net: support feature provisioning

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On 9/26/2022 12:11 AM, Jason Wang wrote:
On Sat, Sep 24, 2022 at 4:01 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:


On 9/21/2022 7:43 PM, Jason Wang wrote:
This patch implements features provisioning for vdpa_sim_net.

1) validating the provisioned features to be a subset of the parent
    features.
2) clearing the features that is not wanted by the userspace

For example:

# vdpa mgmtdev show
vdpasim_net:
   supported_classes net
   max_supported_vqs 3
   dev_features MTU MAC CTRL_VQ CTRL_MAC_ADDR ANY_LAYOUT VERSION_1 ACCESS_PLATFORM
Sighs, not to blame any one and it's perhaps too late, but this
"dev_features" attr in "mgmtdev show" command output should have been
called "supported_features" in the first place.
Not sure I get this, but I guess this is the negotiated features actually.
Actually no, that is why I said the name is a bit confusing and "supported_features" might sound better. This attribute in the parent device (mgmtdev) denotes the real device capability for what virtio features can be supported by the parent device. Any unprivileged user can check into this field to know parent device's capability without having to create a child vDPA device at all. The features that child vDPA device may support should be a subset of, or at most up to what the parent device offers. For e.g. the vdpa device dev1 you created below can expose less or equal device_features bit than 0x308820028 (MTU MAC CTRL_VQ CTRL_MAC_ADDR ANY_LAYOUT VERSION_1 ACCESS_PLATFORM), but shouldn't be no more than what the parent device can actually support.


I think Ling Shan is working on reporting both negotiated features
with the device features.
Does it imply this series is connected to another work in parallel? Is it possible to add a reference in the cover letter?



        
1) provision vDPA device with all features that are supported by the
    net simulator

# vdpa dev add name dev1 mgmtdev vdpasim_net
# vdpa dev config show
dev1: mac 00:00:00:00:00:00 link up link_announce false mtu 1500
   negotiated_features MTU MAC CTRL_VQ CTRL_MAC_ADDR VERSION_1 ACCESS_PLATFORM
Maybe not in this patch, but for completeness for the whole series,
could we also add device_features to the output?
Lingshan, could you please share your thoughts or patch on this?
Noted here the device_features argument specified during vdpa creation is introduced by this series itself, it somehow slightly changed the original semantics of what device_features used to be.


When simply look at the "vdpa dev config show" output, I cannot really
tell the actual device_features that was used in vdpa creation. For e.g.
there is a missing feature ANY_LAYOUT from negotiated_features compared
with supported_features in mgmtdev, but the orchestration software
couldn't tell if the vdpa device on destination host should be created
with or without the ANY_LAYOUT feature.
I think VERSION_1 implies ANY_LAYOUT.
Right, ANY_LAYOUT is a bad example. A good example might be that, I knew the parent mgmtdev on migration source node supports CTRL_MAC_ADDR, but I don't find it in negotiated_features. On the migration destination node, the parent device does support all features as the source offers, including CTRL_MAC_ADDR. What device features you would expect the mgmt software to create destination vdpa device with, if not otherwise requiring mgmt software to remember all the arguments on device creation?

SOURCE# vdpa mgmtdev show
vdpasim_net:
   supported_classes net
   max_supported_vqs 3
   dev_features MTU MAC CTRL_VQ CTRL_MAC_ADDR ANY_LAYOUT VERSION_1 ACCESS_PLATFORM
SOURCE# vdpa dev config show
dev1: mac 00:00:00:00:00:00 link up link_announce false mtu 1500
   negotiated_features MTU MAC CTRL_VQ VERSION_1 ACCESS_PLATFORM

DESTINATION# vdpa mgmtdev show
vdpasim_net:
   supported_classes net
   max_supported_vqs 3
   dev_features MTU MAC CTRL_VQ CTRL_MAC_ADDR ANY_LAYOUT VERSION_1 ACCESS_PLATFORM

 But it should be sufficient to
use features_src & feature_dst in this case. Actually, it should work
similar as to the cpu flags, the management software should introduce
the concept of cluster which means the maximal set of common features
is calculated and provisioned during device creation to allow
migration among the nodes inside the cluster.
Yes, this is one way mgmt software may implement, but I am not sure if it's the only way. For e.g. for cpu flags, mgmt software can infer the guest cpus features in use from all qemu command line arguments and host cpu features/capability, which doesn't need to remember creation arguments and is easy to recover from failure without having to make the VM config persistent in data store. I thought it would be great if vdpa CLI design could offer the same.

Thanks,
-Siwei


Thanks

Thanks,
-Siwei


2) provision vDPA device with a subset of the features

# vdpa dev add name dev1 mgmtdev vdpasim_net device_features 0x300020000
# vdpa dev config show
dev1: mac 00:00:00:00:00:00 link up link_announce false mtu 1500
   negotiated_features CTRL_VQ VERSION_1 ACCESS_PLATFORM

Reviewed-by: Eli Cohen <elic@xxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
  drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 11 ++++++++++-
  1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
index 886449e88502..a9ba02be378b 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
@@ -254,6 +254,14 @@ static int vdpasim_net_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
      dev_attr.work_fn = vdpasim_net_work;
      dev_attr.buffer_size = PAGE_SIZE;

+     if (config->mask & BIT_ULL(VDPA_ATTR_DEV_FEATURES)) {
+             if (config->device_features &
+                 ~dev_attr.supported_features)
+                     return -EINVAL;
+             dev_attr.supported_features &=
+                      config->device_features;
+     }
+
      simdev = vdpasim_create(&dev_attr);
      if (IS_ERR(simdev))
              return PTR_ERR(simdev);
@@ -294,7 +302,8 @@ static struct vdpa_mgmt_dev mgmt_dev = {
      .id_table = id_table,
      .ops = &vdpasim_net_mgmtdev_ops,
      .config_attr_mask = (1 << VDPA_ATTR_DEV_NET_CFG_MACADDR |
-                          1 << VDPA_ATTR_DEV_NET_CFG_MTU),
+                          1 << VDPA_ATTR_DEV_NET_CFG_MTU |
+                          1 << VDPA_ATTR_DEV_FEATURES),
      .max_supported_vqs = VDPASIM_NET_VQ_NUM,
      .supported_features = VDPASIM_NET_FEATURES,
  };

      

    

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