Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201129064351.63618-1-elic@nvidia.com> <20201129150505-mutt-send-email-mst@kernel.org>
 <20201130062746.GA99449@mtl-vdi-166.wap.labs.mlnx> <20201130035147-mutt-send-email-mst@kernel.org>
 <20201130092759.GB99449@mtl-vdi-166.wap.labs.mlnx> <20201130043050-mutt-send-email-mst@kernel.org>
 <CACLfguXB+SzocLppNtrTZwKPFsshS8TLVe8_iFJxgjT-cFpSzA@mail.gmail.com>
 <20201130103142-mutt-send-email-mst@kernel.org> <CACLfguWDFgJUJTJik1obvv-vzacRwgkfsN=-Uouu+K9dAKFE+A@mail.gmail.com>
 <20201201063124-mutt-send-email-mst@kernel.org>
In-Reply-To: <20201201063124-mutt-send-email-mst@kernel.org>
From:   Cindy Lu <lulu@redhat.com>
Date:   Wed, 2 Dec 2020 10:27:02 +0800
Message-ID: <CACLfguUvb-04584jKBnh+9y0KHNn7eqxSAjK6y1OqZMGTsvMKQ@mail.gmail.com>
Subject: Re: [PATCH] vdpa/mlx5: Use random MAC for the vdpa net instance
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Eli Cohen <elic@nvidia.com>, Jason Wang <jasowang@redhat.com>,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Dec 1, 2020 at 7:32 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Dec 01, 2020 at 05:23:18PM +0800, Cindy Lu wrote:
> > On Mon, Nov 30, 2020 at 11:33 PM Michael S. Tsirkin <mst@redhat.com> wr=
ote:
> > >
> > > On Mon, Nov 30, 2020 at 06:41:45PM +0800, Cindy Lu wrote:
> > > > On Mon, Nov 30, 2020 at 5:33 PM Michael S. Tsirkin <mst@redhat.com>=
 wrote:
> > > > >
> > > > > On Mon, Nov 30, 2020 at 11:27:59AM +0200, Eli Cohen wrote:
> > > > > > On Mon, Nov 30, 2020 at 04:00:51AM -0500, Michael S. Tsirkin wr=
ote:
> > > > > > > On Mon, Nov 30, 2020 at 08:27:46AM +0200, Eli Cohen wrote:
> > > > > > > > On Sun, Nov 29, 2020 at 03:08:22PM -0500, Michael S. Tsirki=
n wrote:
> > > > > > > > > On Sun, Nov 29, 2020 at 08:43:51AM +0200, Eli Cohen wrote=
:
> > > > > > > > > > We should not try to use the VF MAC address as that is =
used by the
> > > > > > > > > > regular (e.g. mlx5_core) NIC implementation. Instead, u=
se a random
> > > > > > > > > > generated MAC address.
> > > > > > > > > >
> > > > > > > > > > Suggested by: Cindy Lu <lulu@redhat.com>
> > > > > > > > > > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for su=
pported mlx5 devices")
> > > > > > > > > > Signed-off-by: Eli Cohen <elic@nvidia.com>
> > > > > > > > >
> > > > > > > > > I didn't realise it's possible to use VF in two ways
> > > > > > > > > with and without vdpa.
> > > > > > > >
> > > > > > > > Using a VF you can create quite a few resources, e.g. send =
queues
> > > > > > > > recieve queues, virtio_net queues etc. So you can possibly =
create
> > > > > > > > several instances of vdpa net devices and nic net devices.
> > > > > > > >
> > > > > > > > > Could you include a bit more description on the failure
> > > > > > > > > mode?
> > > > > > > >
> > > > > > > > Well, using the MAC address of the nic vport is wrong since=
 that is the
> > > > > > > > MAC of the regular NIC implementation of mlx5_core.
> > > > > > >
> > > > > > > Right but ATM it doesn't coexist with vdpa so what's the prob=
lem?
> > > > > > >
> > > > > >
> > > > > > This call is wrong:  mlx5_query_nic_vport_mac_address()
> > > > > >
> > > > > > > > > Is switching to a random mac for such an unusual
> > > > > > > > > configuration really justified?
> > > > > > > >
> > > > > > > > Since I can't use the NIC's MAC address, I have two options=
:
> > > > > > > > 1. To get the MAC address as was chosen by the user adminis=
tering the
> > > > > > > >    NIC. This should invoke the set_config callback. Unfortu=
nately this
> > > > > > > >    is not implemented yet.
> > > > > > > >
> > > > > > > > 2. Use a random MAC address. This is OK since if (1) is imp=
lemented it
> > > > > > > >    can always override this random configuration.
> > > > > > > >
> > > > > > > > > It looks like changing a MAC could break some guests,
> > > > > > > > > can it not?
> > > > > > > > >
> > > > > > > >
> > > > > > > > No, it will not. The current version of mlx5 VDPA does not =
allow regular
> > > > > > > > NIC driver and VDPA to co-exist. I have patches ready that =
enable that
> > > > > > > > from steering point of view. I will post them here once oth=
er patches on
> > > > > > > > which they depend will be merged.
> > > > > > > >
> > > > > > > > https://patchwork.ozlabs.org/project/netdev/patch/202011202=
30339.651609-12-saeedm@nvidia.com/
> > > > > > >
> > > > > > > Could you be more explicit on the following points:
> > > > > > > - which configuration is broken ATM (as in, two device have i=
dentical
> > > > > > >   macs? any other issues)?
> > > > > >
> > > > > > The only wrong thing is the call to  mlx5_query_nic_vport_mac_a=
ddress().
> > > > > > It's not breaking anything yet is wrong. The random MAC address=
 setting
> > > > > > is required for the steering patches.
> > > > >
> > > > > Okay so I'm not sure the Fixes tag at least is appropriate if it'=
s a
> > > > > dependency of a new feature.
> > > > >
> > > > > > > - why won't device MAC change from guest point of view?
> > > > > > >
> > > > > >
> > > > > > It's lack of implementation in qemu as far as I know.
> > > > >
> > > > > Sorry not sure I understand. What's not implemented in QEMU?
> > > > >
> > > > HI Michael, there are some bug in qemu to set_config, this will fix=
 in future,
> > > > But this patch is still needed, because without this patch the mlx
> > > > driver will give an 0 mac address to qemu
> > > > and qemu will overwrite the default mac address.  This will cause t=
raffic down.
> > >
> > > Hmm the patch description says VF mac address, not 0 address. Confuse=
d.
> > > If there's no mac we can clear VIRTIO_NET_F_MAC and have guest
> > > use a random value ...
> > >
> > hi Michael=EF=BC=8C
> > I have tried as your suggestion, seems even remove the
> > VIRTIO_NET_F_MAC the qemu will still call get_cinfig and overwrite the
> > default address in  VM,
> > this process is like
> > vdpa _init -->qemu call get_config ->mlx driver will give  an mac
> > address with all 0-->
> > qemu will not check this mac address and use it --> overwrite the mac
> > address in qemu
>
> Right but guest will ignore it then, right?
>
I have tired, but guest will use it, here is some information from guest
[root@localhost ~]# cat /sys/bus/pci/devices/0000\:00\:04.0/virtio0/feature=
s
1110010000011000111100010000000010000000000000000000000000000000
[root@localhost ~]# ifconfig -a
eth0: flags=3D4098<BROADCAST,MULTICAST>  mtu 1500
        ether 00:00:00:00:00:00  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
For my understanding, this NIC should have MAC address by default ,
and this should not depend on
any other function/use case,for driver itself it's incorrect to give
an mac address with all 0 to  qemu without error/fail

Thanks
Cindy
> > So for my understanding there are several method to fix this problem
> >
> > 1, qemu check the mac address, if the mac address is all 0, qemu will
> > ignore it and set the random mac address to mlx driver.
> > 2. mlx driver checks the mac address and if this mac is 0, return fail
> > to qemu, but this need to change the UAPI.
> > 3. mlx driver it shelf should get an correct mac address while it init.
> > 4. add check in qemu get_config function  , if there is not F_MAC Then
> > ignore the mac address from mlx driver
> >
> > not sure which method is more suitable ?
> >
> > Thanks
> > Cindy
> >
> >
> >
> > > > > > >
> > > > > > > > > > ---
> > > > > > > > > >  drivers/vdpa/mlx5/net/mlx5_vnet.c | 5 +----
> > > > > > > > > >  1 file changed, 1 insertion(+), 4 deletions(-)
> > > > > > > > > >
> > > > > > > > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/driver=
s/vdpa/mlx5/net/mlx5_vnet.c
> > > > > > > > > > index 1fa6fcac8299..80d06d958b8b 100644
> > > > > > > > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > > > > > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > > > > > > > > @@ -1955,10 +1955,7 @@ void *mlx5_vdpa_add_dev(struct m=
lx5_core_dev *mdev)
> > > > > > > > > >       if (err)
> > > > > > > > > >               goto err_mtu;
> > > > > > > > > >
> > > > > > > > > > -     err =3D mlx5_query_nic_vport_mac_address(mdev, 0,=
 0, config->mac);
> > > > > > > > > > -     if (err)
> > > > > > > > > > -             goto err_mtu;
> > > > > > > > > > -
> > > > > > > > > > +     eth_random_addr(config->mac);
> > > > > > > > > >       mvdev->vdev.dma_dev =3D mdev->device;
> > > > > > > > > >       err =3D mlx5_vdpa_alloc_resources(&ndev->mvdev);
> > > > > > > > > >       if (err)
> > > > > > > > > > --
> > > > > > > > > > 2.26.2
> > > > > > > > >
> > > > > > >
> > > > >
> > >
>