netdev - Re: [PATCH V2 RESEND 1/6] vDPA: allow userspace to query features of a vDPA device

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Date:   Tue, 27 Sep 2022 18:02:14 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH V2 RESEND 1/6] vDPA: allow userspace to query features of
 a vDPA device



On 9/27/2022 12:36 PM, Jason Wang wrote:
> On Tue, Sep 27, 2022 at 11:09 AM Zhu Lingshan <lingshan.zhu@...el.com> wrote:
>> This commit adds a new vDPA netlink attribution
>> VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES. Userspace can query
>> features of vDPA devices through this new attr.
>>
>> This commit invokes vdpa_config_ops.get_config()
>> rather than vdpa_get_config_unlocked() to read
>> the device config spcae, so no races in
>> vdpa_set_features_unlocked()
>>
>> Userspace tool iproute2 example:
>> $ vdpa dev config show vdpa0
>> vdpa0: mac 00:e8:ca:11:be:05 link up link_announce false max_vq_pairs 4 mtu 1500
>>    negotiated_features MRG_RXBUF CTRL_VQ MQ VERSION_1 ACCESS_PLATFORM
>>    dev_features MTU MAC MRG_RXBUF CTRL_VQ MQ ANY_LAYOUT VERSION_1 ACCESS_PLATFORM
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>> ---
>>   drivers/vdpa/vdpa.c       | 17 ++++++++++++-----
>>   include/uapi/linux/vdpa.h |  4 ++++
>>   2 files changed, 16 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
>> index c06c02704461..2035700d6fc8 100644
>> --- a/drivers/vdpa/vdpa.c
>> +++ b/drivers/vdpa/vdpa.c
>> @@ -491,6 +491,7 @@ static int vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *m
>>                  err = -EMSGSIZE;
>>                  goto msg_err;
>>          }
>> +
> Nit: Unnecessary changes.
oh, yes!
>
>>          if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_SUPPORTED_FEATURES,
>>                                mdev->supported_features, VDPA_ATTR_PAD)) {
>>                  err = -EMSGSIZE;
>> @@ -815,10 +816,10 @@ static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
>>   static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
>>   {
>>          struct virtio_net_config config = {};
>> -       u64 features;
>> +       u64 features_device, features_driver;
>>          u16 val_u16;
>>
>> -       vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
>> +       vdev->config->get_config(vdev, 0, &config, sizeof(config));
>>
>>          if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
>>                      config.mac))
>> @@ -832,12 +833,18 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>>          if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
>>                  return -EMSGSIZE;
>>
>> -       features = vdev->config->get_driver_features(vdev);
>> -       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features,
>> +       features_driver = vdev->config->get_driver_features(vdev);
>> +       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
>> +                             VDPA_ATTR_PAD))
>> +               return -EMSGSIZE;
> It looks to me that those parts were removed in patch 2. I wonder if
> it's better to reorder the patch to let patch 2 come first?
I am not sure, if we apply patch 2(check FEATURES_OK in 
vdpa_dev_config_fill and report driver features there) first,
we need to remove driver_features in vdpa_dev_net_config_fill(),
however, we still not introduce and initialize device features(which is 
in patch 1, introduce device_features) yet,
so the last line "return vdpa_dev_net_mq_config_fill()" which needs 
features as its parameter may not work,
filling NULL looks worse than keep features_driver here.

Thanks
Zhu Lingshan
>
> Thanks
>
>> +
>> +       features_device = vdev->config->get_device_features(vdev);
>> +
>> +       if (nla_put_u64_64bit(msg, VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES, features_device,
>>                                VDPA_ATTR_PAD))
>>                  return -EMSGSIZE;
>>
>> -       return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
>> +       return vdpa_dev_net_mq_config_fill(vdev, msg, features_driver, &config);
>>   }
>>
>>   static int
>> diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
>> index 25c55cab3d7c..07474183fdb3 100644
>> --- a/include/uapi/linux/vdpa.h
>> +++ b/include/uapi/linux/vdpa.h
>> @@ -46,12 +46,16 @@ enum vdpa_attr {
>>
>>          VDPA_ATTR_DEV_NEGOTIATED_FEATURES,      /* u64 */
>>          VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,          /* u32 */
>> +       /* virtio features that are supported by the vDPA management device */
>>          VDPA_ATTR_DEV_SUPPORTED_FEATURES,       /* u64 */
>>
>>          VDPA_ATTR_DEV_QUEUE_INDEX,              /* u32 */
>>          VDPA_ATTR_DEV_VENDOR_ATTR_NAME,         /* string */
>>          VDPA_ATTR_DEV_VENDOR_ATTR_VALUE,        /* u64 */
>>
>> +       /* virtio features that are supported by the vDPA device */
>> +       VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,  /* u64 */
>> +
>>          /* new attributes must be added above here */
>>          VDPA_ATTR_MAX,
>>   };
>> --
>> 2.31.1
>>