From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "Zhu, Lingshan" <lingshan.zhu@intel.com>,
Parav Pandit <parav@nvidia.com>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"xieyongji@bytedance.com" <xieyongji@bytedance.com>,
"gautam.dawar@amd.com" <gautam.dawar@amd.com>
Subject: Re: [PATCH V3 5/6] vDPA: answer num of queue pairs = 1 to userspace when VIRTIO_NET_F_MQ == 0
Date: Mon, 1 Aug 2022 12:50:42 +0800 [thread overview]
Message-ID: <CACGkMEvO4cHE-_0nvT6oe6GmXukcpT=yZGM9SGpVGhjuxnTvTQ@mail.gmail.com> (raw)
In-Reply-To: <20220728024111-mutt-send-email-mst@kernel.org>
On Thu, Jul 28, 2022 at 2:41 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, Jul 28, 2022 at 01:53:51PM +0800, Jason Wang wrote:
> > On Thu, Jul 28, 2022 at 11:47 AM Zhu, Lingshan <lingshan.zhu@intel.com> wrote:
> > >
> > >
> > >
> > > On 7/28/2022 9:21 AM, Jason Wang wrote:
> > > > On Wed, Jul 27, 2022 at 11:45 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >> On Wed, Jul 27, 2022 at 05:50:59PM +0800, Jason Wang wrote:
> > > >>> On Wed, Jul 27, 2022 at 5:03 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >>>> On Wed, Jul 27, 2022 at 02:54:13PM +0800, Jason Wang wrote:
> > > >>>>> On Wed, Jul 27, 2022 at 2:01 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >>>>>> On Wed, Jul 27, 2022 at 03:47:35AM +0000, Parav Pandit wrote:
> > > >>>>>>>> From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > > >>>>>>>> Sent: Tuesday, July 26, 2022 10:53 PM
> > > >>>>>>>>
> > > >>>>>>>> On 7/27/2022 10:17 AM, Parav Pandit wrote:
> > > >>>>>>>>>> From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > > >>>>>>>>>> Sent: Tuesday, July 26, 2022 10:15 PM
> > > >>>>>>>>>>
> > > >>>>>>>>>> On 7/26/2022 11:56 PM, Parav Pandit wrote:
> > > >>>>>>>>>>>> From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > > >>>>>>>>>>>> Sent: Tuesday, July 12, 2022 11:46 PM
> > > >>>>>>>>>>>>> When the user space which invokes netlink commands, detects that
> > > >>>>>>>>>> _MQ
> > > >>>>>>>>>>>> is not supported, hence it takes max_queue_pair = 1 by itself.
> > > >>>>>>>>>>>> I think the kernel module have all necessary information and it is
> > > >>>>>>>>>>>> the only one which have precise information of a device, so it
> > > >>>>>>>>>>>> should answer precisely than let the user space guess. The kernel
> > > >>>>>>>>>>>> module should be reliable than stay silent, leave the question to
> > > >>>>>>>>>>>> the user space
> > > >>>>>>>>>> tool.
> > > >>>>>>>>>>> Kernel is reliable. It doesn’t expose a config space field if the
> > > >>>>>>>>>>> field doesn’t
> > > >>>>>>>>>> exist regardless of field should have default or no default.
> > > >>>>>>>>>> so when you know it is one queue pair, you should answer one, not try
> > > >>>>>>>>>> to guess.
> > > >>>>>>>>>>> User space should not guess either. User space gets to see if _MQ
> > > >>>>>>>>>> present/not present. If _MQ present than get reliable data from kernel.
> > > >>>>>>>>>>> If _MQ not present, it means this device has one VQ pair.
> > > >>>>>>>>>> it is still a guess, right? And all user space tools implemented this
> > > >>>>>>>>>> feature need to guess
> > > >>>>>>>>> No. it is not a guess.
> > > >>>>>>>>> It is explicitly checking the _MQ feature and deriving the value.
> > > >>>>>>>>> The code you proposed will be present in the user space.
> > > >>>>>>>>> It will be uniform for _MQ and 10 other features that are present now and
> > > >>>>>>>> in the future.
> > > >>>>>>>> MQ and other features like RSS are different. If there is no _RSS_XX, there
> > > >>>>>>>> are no attributes like max_rss_key_size, and there is not a default value.
> > > >>>>>>>> But for MQ, we know it has to be 1 wihtout _MQ.
> > > >>>>>>> "we" = user space.
> > > >>>>>>> To keep the consistency among all the config space fields.
> > > >>>>>> Actually I looked and the code some more and I'm puzzled:
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> struct virtio_net_config config = {};
> > > >>>>>> u64 features;
> > > >>>>>> u16 val_u16;
> > > >>>>>>
> > > >>>>>> vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
> > > >>>>>>
> > > >>>>>> if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
> > > >>>>>> config.mac))
> > > >>>>>> return -EMSGSIZE;
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> Mac returned even without VIRTIO_NET_F_MAC
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> val_u16 = le16_to_cpu(config.status);
> > > >>>>>> if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16))
> > > >>>>>> return -EMSGSIZE;
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> status returned even without VIRTIO_NET_F_STATUS
> > > >>>>>>
> > > >>>>>> val_u16 = le16_to_cpu(config.mtu);
> > > >>>>>> if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
> > > >>>>>> return -EMSGSIZE;
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> MTU returned even without VIRTIO_NET_F_MTU
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> What's going on here?
> > > >>>>> Probably too late to fix, but this should be fine as long as all
> > > >>>>> parents support STATUS/MTU/MAC.
> > > >>>> Why is this too late to fix.
> > > >>> If we make this conditional on the features. This may break the
> > > >>> userspace that always expects VDPA_ATTR_DEV_NET_CFG_MTU?
> > > >>>
> > > >>> Thanks
> > > >> Well only on devices without MTU. I'm saying said userspace
> > > >> was reading trash on such devices anyway.
> > > > It depends on the parent actually. For example, mlx5 query the lower
> > > > mtu unconditionally:
> > > >
> > > > err = query_mtu(mdev, &mtu);
> > > > if (err)
> > > > goto err_alloc;
> > > >
> > > > ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, mtu);
> > > >
> > > > Supporting MTU features seems to be a must for real hardware.
> > > > Otherwise the driver may not work correctly.
> > > >
> > > >> We don't generally maintain bug for bug compatiblity on a whim,
> > > >> only if userspace is actually known to break if we fix a bug.
> > > > So I think it should be fine to make this conditional then we should
> > > > have a consistent handling of other fields like MQ.
> > > For some fields that have a default value, like MQ =1, we can return the
> > > default value.
> > > For other fields without a default value, like MAC, we return nothing.
> > >
> > > Does this sounds good? So, for MTU, if without _F_MTU, I think we can
> > > return 1500 by default.
> >
> > Or we can just read MTU from the device.
> >
> > But It looks to me Michael wants it conditional.
> >
> > Thanks
>
> I'm fine either way but let's keep it consistent. And I think
> Parav wants it conditional.
Parav, what's your opinion here?
Michale spots some in-consistent stuffs, so I think we should either
1) make all conditional, so we should change both MTU and MAC
or
2) make them unconditional, so we should only change MQ
Thanks
>
> > >
> > > Thanks,
> > > Zhu Lingshan
> > > >
> > > > Thanks
> > > >
> > > >>
> > > >>>>> I wonder if we can add a check in the core and fail the device
> > > >>>>> registration in this case.
> > > >>>>>
> > > >>>>> Thanks
> > > >>>>>
> > > >>>>>>
> > > >>>>>> --
> > > >>>>>> MST
> > > >>>>>>
> > >
>
next prev parent reply other threads:[~2022-08-01 4:51 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-01 13:28 [PATCH V3 0/6] ifcvf/vDPA: support query device config space through netlink Zhu Lingshan
2022-07-01 13:28 ` [PATCH V3 1/6] vDPA/ifcvf: get_config_size should return a value no greater than dev implementation Zhu Lingshan
2022-07-04 4:39 ` Jason Wang
2022-07-08 6:44 ` Zhu, Lingshan
2022-07-13 5:44 ` Michael S. Tsirkin
2022-07-13 7:52 ` Zhu, Lingshan
2022-07-13 5:31 ` Michael S. Tsirkin
2022-07-13 7:48 ` Zhu, Lingshan
2022-07-01 13:28 ` [PATCH V3 2/6] vDPA/ifcvf: support userspace to query features and MQ of a management device Zhu Lingshan
2022-07-04 4:43 ` Jason Wang
2022-07-08 6:54 ` Zhu, Lingshan
2022-07-01 13:28 ` [PATCH V3 3/6] vDPA: allow userspace to query features of a vDPA device Zhu Lingshan
2022-07-01 22:02 ` Parav Pandit
2022-07-04 4:46 ` Jason Wang
2022-07-04 12:53 ` Parav Pandit
2022-07-05 7:59 ` Zhu, Lingshan
2022-07-05 11:56 ` Parav Pandit
2022-07-05 16:56 ` Zhu, Lingshan
2022-07-05 17:01 ` Parav Pandit
2022-07-06 2:25 ` Zhu, Lingshan
2022-07-06 2:28 ` Parav Pandit
2022-07-23 11:27 ` Zhu, Lingshan
2022-07-24 15:23 ` Parav Pandit
2022-07-27 8:15 ` Si-Wei Liu
2022-07-27 11:38 ` Zhu, Lingshan
2022-07-08 6:16 ` Zhu, Lingshan
2022-07-08 16:13 ` Parav Pandit
2022-07-11 2:18 ` Zhu, Lingshan
2022-07-01 13:28 ` [PATCH V3 4/6] vDPA: !FEATURES_OK should not block querying device config space Zhu Lingshan
2022-07-01 22:12 ` Parav Pandit
2022-07-08 6:22 ` Zhu, Lingshan
2022-07-13 5:23 ` Michael S. Tsirkin
2022-07-13 7:46 ` Zhu, Lingshan
[not found] ` <00889067-50ac-d2cd-675f-748f171e5c83@oracle.com>
[not found] ` <63242254-ba84-6810-dad8-34f900b97f2f@intel.com>
[not found] ` <8002554a-a77c-7b25-8f99-8d68248a741d@oracle.com>
2022-07-28 2:06 ` Jason Wang
2022-07-28 7:08 ` Si-Wei Liu
2022-07-28 7:36 ` Jason Wang
2022-07-28 7:44 ` Zhu, Lingshan
[not found] ` <2dfff5f3-3100-4a63-6da3-3e3d21ffb364@oracle.com>
2022-07-28 11:28 ` spec clarification (was Re: [PATCH V3 4/6] vDPA: !FEATURES_OK should not block querying device config space) Michael S. Tsirkin
2022-07-28 11:35 ` [PATCH V3 4/6] vDPA: !FEATURES_OK should not block querying device config space Michael S. Tsirkin
2022-07-28 22:12 ` Si-Wei Liu
[not found] ` <00e2e07e-1a2e-7af8-a060-cc9034e0d33f@intel.com>
[not found] ` <b58dba25-3258-d600-ea06-879094639852@oracle.com>
[not found] ` <c143e2da-208e-b046-9b8f-1780f75ed3e6@intel.com>
2022-07-29 20:55 ` Si-Wei Liu
2022-08-01 4:44 ` Jason Wang
2022-08-01 22:53 ` Si-Wei Liu
2022-08-01 22:58 ` Si-Wei Liu
2022-08-02 6:33 ` Jason Wang
2022-08-03 1:26 ` Si-Wei Liu
2022-08-03 2:30 ` Zhu, Lingshan
2022-08-03 23:09 ` Si-Wei Liu
2022-08-04 1:41 ` Zhu, Lingshan
2022-08-04 1:41 ` Zhu, Lingshan
2022-07-01 13:28 ` [PATCH V3 5/6] vDPA: answer num of queue pairs = 1 to userspace when VIRTIO_NET_F_MQ == 0 Zhu Lingshan
2022-07-01 22:07 ` Parav Pandit
2022-07-08 6:21 ` Zhu, Lingshan
2022-07-08 16:23 ` Parav Pandit
2022-07-11 2:29 ` Zhu, Lingshan
2022-07-12 16:48 ` Parav Pandit
2022-07-13 3:03 ` Zhu, Lingshan
2022-07-13 3:06 ` Parav Pandit
2022-07-13 3:45 ` Zhu, Lingshan
2022-07-26 15:56 ` Parav Pandit
2022-07-26 19:52 ` Michael S. Tsirkin
2022-07-26 20:49 ` Parav Pandit
2022-07-27 2:14 ` Zhu, Lingshan
2022-07-27 2:17 ` Parav Pandit
2022-07-27 2:53 ` Zhu, Lingshan
2022-07-27 3:47 ` Parav Pandit
2022-07-27 4:24 ` Zhu, Lingshan
2022-07-27 6:01 ` Michael S. Tsirkin
2022-07-27 6:25 ` Zhu, Lingshan
2022-07-27 6:56 ` Jason Wang
2022-07-27 9:05 ` Michael S. Tsirkin
2022-07-27 6:54 ` Jason Wang
2022-07-27 9:02 ` Michael S. Tsirkin
2022-07-27 9:50 ` Jason Wang
2022-07-27 15:45 ` Michael S. Tsirkin
2022-07-28 1:21 ` Jason Wang
2022-07-28 3:46 ` Zhu, Lingshan
2022-07-28 5:53 ` Jason Wang
2022-07-28 6:02 ` Zhu, Lingshan
2022-07-28 6:41 ` Michael S. Tsirkin
2022-08-01 4:50 ` Jason Wang [this message]
2022-07-27 7:50 ` Si-Wei Liu
2022-07-27 9:01 ` Michael S. Tsirkin
2022-07-27 10:09 ` Si-Wei Liu
2022-07-27 11:54 ` Zhu, Lingshan
2022-07-28 1:41 ` Si-Wei Liu
2022-07-28 2:44 ` Zhu, Lingshan
2022-07-28 21:54 ` Si-Wei Liu
2022-07-29 2:07 ` Zhu, Lingshan
2022-07-27 15:48 ` Michael S. Tsirkin
2022-07-13 5:26 ` Michael S. Tsirkin
2022-07-13 7:47 ` Zhu, Lingshan
2022-07-26 15:54 ` Parav Pandit
2022-07-26 19:48 ` Michael S. Tsirkin
2022-07-26 20:53 ` Parav Pandit
2022-07-27 1:56 ` Zhu, Lingshan
2022-07-27 2:11 ` Zhu, Lingshan
2022-07-01 13:28 ` [PATCH V3 6/6] vDPA: fix 'cast to restricted le16' warnings in vdpa.c Zhu Lingshan
2022-07-01 22:18 ` Parav Pandit
2022-07-08 6:25 ` Zhu, Lingshan
2022-07-08 16:08 ` Parav Pandit
2022-07-29 8:53 ` Michael S. Tsirkin
2022-07-29 9:07 ` Zhu, Lingshan
2022-07-29 9:17 ` Michael S. Tsirkin
2022-07-29 9:20 ` Zhu, Lingshan
2022-07-29 9:23 ` Michael S. Tsirkin
2022-07-29 9:35 ` Zhu, Lingshan
2022-07-29 9:39 ` Michael S. Tsirkin
2022-07-29 10:01 ` Zhu, Lingshan
2022-07-29 10:16 ` Michael S. Tsirkin
2022-07-29 10:18 ` Zhu, Lingshan
2022-08-01 4:33 ` Jason Wang
2022-08-01 6:25 ` Michael S. Tsirkin
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