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<f63698fc-21eb-64b0-94b7-3e605ea725cd@intel.com> <3166646.G96rZvMJ2N@thomas>
<6aed79d2-be6c-7f30-a562-7acd69ebae57@intel.com>
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From: kumaraparameshwaran rathinavel <kumaraparamesh92@gmail.com>
Date: Tue, 18 Jan 2022 16:51:18 +0530
Message-ID: <CANxNyatvCNNC35idXfqSZekE-z6H2LCchXFCuzYKcCAhqEyBWw@mail.gmail.com>
Subject: Re: [PATCH] net/tap: Bug fix to populate fds in secondary process
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Thomas Monjalon <thomas@monjalon.net>, "Wiles,
Keith" <keith.wiles@intel.com>, dev@dpdk.org,
Kumara Parameshwaran <kparameshwar@vmware.com>,
Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
David Marchand <david.marchand@redhat.com>
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Just wanted to bring it to your attention,
In Mellanox driver there is a requirement to exchange fds between primary
and secondary and similar usage is seen, the primary sends the port_id and
the secondary refers to the rte_eth_devices in the driver,
The functions are
- mlx5_mp_secondary_handle in secondary
- mlx5_mp_req_start_rxtx in primary which is invoked from
mlx5_dev_start.
In my implementation I have used the name and invoked get_port_by_name, I
can also pass the port_id from the primary to make it uniform. So with
similar usage in Mellanox is there a problem there as well on referring to
the rte_eth_devices from the PMD ?
On Tue, Jan 18, 2022 at 3:17 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> On 1/17/2022 6:33 PM, Thomas Monjalon wrote:
> > 17/01/2022 19:28, Ferruh Yigit:
> >>> + ret = rte_eth_dev_get_port_by_name(request_param->port_name,
> &port_id);
> >>> + if (ret) {
> >>> + TAP_LOG(ERR, "Failed to get port id for %s",
> >>> + request_param->port_name);
> >>> + return -1;
> >>> + }
> >>> + dev = &rte_eth_devices[port_id];
> >>
> >> Since this is not really related with your patch, I want to have a
> separate thread for it.
> >>
> >> It is not good to access the 'rte_eth_devices' global variable directly
> from a driver, that
> >> is error prone.
> >>
> >> Btw, what 'peer' supposed to contain?
> >>
> >> It can be solved by adding an internal API, only for drivers to get
> eth_dev from the name,
> >> like: 'rte_eth_dev_get_by_name()'.
> >> This way a few other usage can be converted to this API.
> >>
> >> @Thomas and @Andrew what do you think about the new API proposal?
> >
> > It looks similar to rte_eth_dev_get_port_by_name() which returns a
> port_id.
>
> Exactly, but get eth_dev directly for drivers. For drivers no need to work
> with port_id
> handler, they can use eth_dev directly.
>
> Another solution can be an getter function for drivers, which gets port_id
> and returns
> the eth_dev.
>
> > It is a bit strange for an ethdev driver to not have access to its own
> ethdev struct.
> > Isn't there something broken in the logic?
> >
>
> This is callback function between primary and secondary applications sync.
> So port name
> will be same for both, but eth_dev will be different and port_id may be
> different.
> Driver finds its own eth_dev from the shared port name.
>
>
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Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr"><div>Just wanted to bring it to your attention,</div><div>=
<br></div><div>In Mellanox driver there is a requirement to exchange fds be=
tween primary and secondary and similar usage is seen, the primary sends th=
e port_id and the secondary refers to the rte_eth_devices in the driver, <b=
r></div><div>The functions are <br></div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - mlx5_mp_secondary_handle in secondary <=
br></div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =
- mlx5_mp_req_start_rxtx in primary which is invoked from mlx5_dev_start. <=
br></div><div><br></div><div>In my implementation I have used the name and =
invoked get_port_by_name, I can also pass the port_id from the primary to m=
ake it uniform. So with similar usage in Mellanox is there a problem there =
as well on referring to the rte_eth_devices from the PMD ? <br></div><div><=
br></div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gma=
il_attr">On Tue, Jan 18, 2022 at 3:17 PM Ferruh Yigit <<a href=3D"mailto=
:ferruh.yigit@intel.com">ferruh.yigit@intel.com</a>> wrote:<br></div><bl=
ockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-lef=
t:1px solid rgb(204,204,204);padding-left:1ex">On 1/17/2022 6:33 PM, Thomas=
Monjalon wrote:<br>
> 17/01/2022 19:28, Ferruh Yigit:<br>
>>> +=C2=A0 =C2=A0ret =3D rte_eth_dev_get_port_by_name(request_par=
am->port_name, &port_id);<br>
>>> +=C2=A0 =C2=A0if (ret) {<br>
>>> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0TAP_LOG(ERR, "F=
ailed to get port id for %s",<br>
>>> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0request_param->port_name);<br>
>>> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return -1;<br>
>>> +=C2=A0 =C2=A0}<br>
>>> +=C2=A0 =C2=A0dev =3D &rte_eth_devices[port_id];<br>
>><br>
>> Since this is not really related with your patch, I want to have a=
separate thread for it.<br>
>><br>
>> It is not good to access the 'rte_eth_devices' global vari=
able directly from a driver, that<br>
>> is error prone.<br>
>><br>
>> Btw, what 'peer' supposed to contain?<br>
>><br>
>> It can be solved by adding an internal API, only for drivers to ge=
t eth_dev from the name,<br>
>> like: 'rte_eth_dev_get_by_name()'.<br>
>> This way a few other usage can be converted to this API.<br>
>><br>
>> @Thomas and @Andrew what do you think about the new API proposal?<=
br>
> <br>
> It looks similar to rte_eth_dev_get_port_by_name() which returns a por=
t_id.<br>
<br>
Exactly, but get eth_dev directly for drivers. For drivers no need to work =
with port_id<br>
handler, they can use eth_dev directly.<br>
<br>
Another solution can be an getter function for drivers, which gets port_id =
and returns<br>
the eth_dev.<br>
<br>
> It is a bit strange for an ethdev driver to not have access to its own=
ethdev struct.<br>
> Isn't there something broken in the logic?<br>
> <br>
<br>
This is callback function between primary and secondary applications sync. =
So port name<br>
will be same for both, but eth_dev will be different and port_id may be dif=
ferent.<br>
Driver finds its own eth_dev from the shared port name.<br>
<br>
</blockquote></div>
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