netdev - Re: [PATCH] iproute2/vdpa: Add support for reading device features

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Date:   Tue, 18 Oct 2022 15:46:10 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, stephen@...workplumber.org, dsahern@...nel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        hang.yuan@...el.com
Subject: Re: [PATCH] iproute2/vdpa: Add support for reading device features



On 10/18/2022 3:30 PM, Jason Wang wrote:
> On Tue, Oct 18, 2022 at 3:28 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>>
>>
>> On 10/18/2022 2:44 PM, Jason Wang wrote:
>>> On Tue, Oct 18, 2022 at 10:20 AM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>>>>
>>>> On 10/17/2022 3:13 PM, Jason Wang wrote:
>>>>> On Mon, Oct 17, 2022 at 3:13 PM Jason Wang <jasowang@...hat.com> wrote:
>>>>>> On Fri, Oct 14, 2022 at 5:50 PM Zhu Lingshan <lingshan.zhu@...el.com> wrote:
>>>>>>> This commit implements support for reading vdpa device
>>>>>>> features in 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>
>>>>>> Note that Si Wei proposed to unify the two new attributes:
>>>>> https://patchew.org/linux/1665422823-18364-1-git-send-email-si-wei.liu@oracle.com/
>>>> I think we have discussed this before, there should be two netlink
>>>> attributes to report management device features and vDPA device features,
>>>> they are different type of devices, this unification introduces
>>>> unnecessary couplings
>>> I suggest going through the above patch, both attributes are for the
>>> vDPA device only.
>> It seems not vDPA device only, from above patch, we see it re-uses
>> VDPA_ATTR_DEV_FEATURES for reporting vDPA device features
> Yes, anything wrong with this? The device features could be
> provisioned via netlink.
I think the best netlink practice is to let every attr has its own
and unique purpose, to prevent potential bugs. I think we have discussed 
this before that re-using
an attr does not save any resource.

And iprout2 has already updated the uapi header.

Thanks
>
> Thanks
>
>> Thanks
>>> Thanks
>>>
>>>> Thanks
>>>>> Thanks
>>>>>
>>>>>>> ---
>>>>>>>     vdpa/vdpa.c | 15 +++++++++++++--
>>>>>>>     1 file changed, 13 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/vdpa/vdpa.c b/vdpa/vdpa.c
>>>>>>> index b73e40b4..89844e92 100644
>>>>>>> --- a/vdpa/vdpa.c
>>>>>>> +++ b/vdpa/vdpa.c
>>>>>>> @@ -87,6 +87,8 @@ static const enum mnl_attr_data_type vdpa_policy[VDPA_ATTR_MAX + 1] = {
>>>>>>>            [VDPA_ATTR_DEV_NEGOTIATED_FEATURES] = MNL_TYPE_U64,
>>>>>>>            [VDPA_ATTR_DEV_MGMTDEV_MAX_VQS] = MNL_TYPE_U32,
>>>>>>>            [VDPA_ATTR_DEV_SUPPORTED_FEATURES] = MNL_TYPE_U64,
>>>>>>> +       [VDPA_ATTR_DEV_FEATURES] = MNL_TYPE_U64,
>>>>>>> +       [VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES] = MNL_TYPE_U64,
>>>>>>>     };
>>>>>>>
>>>>>>>     static int attr_cb(const struct nlattr *attr, void *data)
>>>>>>> @@ -482,7 +484,7 @@ static const char * const *dev_to_feature_str[] = {
>>>>>>>
>>>>>>>     #define NUM_FEATURE_BITS 64
>>>>>>>
>>>>>>> -static void print_features(struct vdpa *vdpa, uint64_t features, bool mgmtdevf,
>>>>>>> +static void print_features(struct vdpa *vdpa, uint64_t features, bool devf,
>>>>>>>                               uint16_t dev_id)
>>>>>>>     {
>>>>>>>            const char * const *feature_strs = NULL;
>>>>>>> @@ -492,7 +494,7 @@ static void print_features(struct vdpa *vdpa, uint64_t features, bool mgmtdevf,
>>>>>>>            if (dev_id < ARRAY_SIZE(dev_to_feature_str))
>>>>>>>                    feature_strs = dev_to_feature_str[dev_id];
>>>>>>>
>>>>>>> -       if (mgmtdevf)
>>>>>>> +       if (devf)
>>>>>>>                    pr_out_array_start(vdpa, "dev_features");
>>>>>>>            else
>>>>>>>                    pr_out_array_start(vdpa, "negotiated_features");
>>>>>>> @@ -771,6 +773,15 @@ static void pr_out_dev_net_config(struct vdpa *vdpa, struct nlattr **tb)
>>>>>>>                    val_u64 = mnl_attr_get_u64(tb[VDPA_ATTR_DEV_NEGOTIATED_FEATURES]);
>>>>>>>                    print_features(vdpa, val_u64, false, dev_id);
>>>>>>>            }
>>>>>>> +       if (tb[VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES]) {
>>>>>>> +               uint16_t dev_id = 0;
>>>>>>> +
>>>>>>> +               if (tb[VDPA_ATTR_DEV_ID])
>>>>>>> +                       dev_id = mnl_attr_get_u32(tb[VDPA_ATTR_DEV_ID]);
>>>>>>> +
>>>>>>> +               val_u64 = mnl_attr_get_u64(tb[VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES]);
>>>>>>> +               print_features(vdpa, val_u64, true, dev_id);
>>>>>>> +       }
>>>>>>>     }
>>>>>>>
>>>>>>>     static void pr_out_dev_config(struct vdpa *vdpa, struct nlattr **tb)
>>>>>>> --
>>>>>>> 2.31.1
>>>>>>>