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

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Message-ID: <CACGkMEvcR+PBbnaMpy0CKteNy-HD=42cySEXceSA2iefC2YDLg@mail.gmail.com>
Date:   Tue, 18 Oct 2022 16:00:44 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Zhu, Lingshan" <lingshan.zhu@...el.com>
Cc:     mst@...hat.com, stephen@...workplumber.org, dsahern@...nel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        hang.yuan@...el.com, Si-Wei Liu <si-wei.liu@...cle.com>
Subject: Re: [PATCH] iproute2/vdpa: Add support for reading device features

On Tue, Oct 18, 2022 at 3:55 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
>
>
>
> On 10/18/2022 3:49 PM, Jason Wang wrote:
> > On Tue, Oct 18, 2022 at 3:46 PM Zhu, Lingshan <lingshan.zhu@...el.com> wrote:
> >>
> >>
> >> 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.
> > They have exactly the same semantic which is the device features for vDPA.
> >
> > VDPA_ATTR_DEV_FEATURES is introduced by my features provisioning
> > series, which is used for the userspace to "set" the device features.
> > VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES is introduced in one of your
> > previous patches, which is used for userspace to "get" the device
> > features.
> so basically we are just combining and renaming the attr,
> if so, fine with me, get and set may never conflict and in
> totally different netlink contexts.

Yes, I think so.

Thanks

>
> Thanks
> >
> >> And iprout2 has already updated the uapi header.
> > Yes, but iproute2 has the same schedule as kernel release, so it's not
> > too late to fix.
> >
> > Thanks
> >
> >> 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
> >>>>>>>>>
>