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From: Ophir Munk <ophirmu@mellanox.com>
To: Thomas Monjalon <thomas@monjalon.net>, "dev@dpdk.org" <dev@dpdk.org>
CC: "gaetan.rivet@6wind.com" <gaetan.rivet@6wind.com>, Olga Shern
<olgas@mellanox.com>, Shahaf Shuler <shahafs@mellanox.com>, Asaf Penso
<asafp@mellanox.com>
Thread-Topic: [dpdk-dev] [RFC] eal: allow hotplug to skip an already probed
device
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Date: Thu, 13 Sep 2018 06:29:39 +0000
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Subject: Re: [dpdk-dev] [RFC] eal: allow hotplug to skip an already probed
device
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> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Saturday, September 08, 2018 2:10 AM
> To: dev@dpdk.org
> Cc: gaetan.rivet@6wind.com
> Subject: [dpdk-dev] [RFC] eal: allow hotplug to skip an already probed de=
vice
>=20
> In the devargs syntax for device representors, it is possible to add seve=
ral
> devices at once: -w dbdf,representor=3D[0-3] It will become a more freque=
nt
> case when introducing wildcards and ranges in the new devargs syntax.
>=20
> If a devargs string is provided for probing, and updated with a bigger ra=
nge
> for a new probing, then we do not want it to fail because part of this ra=
nge
> was already probed previously.
>=20
When having devargs with representors ("dbdf,representor=3D<args>") there i=
s actually just one PCI device to probe (whose address is "dbdf", the maste=
r) while the representors themselves are net devices all using the same PCI=
"dbdf" address.=20
The way to see it: when running "lspci": only the "dpdf" PCI device appears=
while when executing "ifconfig" - all representors are shown as net device=
s.
When calling rte_eal_hotplug_add() for the first time there is a flow which=
eventually calls the PMD probe callback (e.g. mlx5_pci_probe() in case of =
mlx5 PMD).=20
When calling rte_eal_hotplug_add() for several times we should skip failure=
s till we reach the PMD probe callback.
Skipping failures can be done as follows:
1. In file ./lib/librte_eal/common/eal_common_dev.c, function: rte_eal_hotp=
lug_add(), remove the following code:
if (dev->driver !=3D NULL) {
RTE_LOG(ERR, EAL, "Device is already plugged\n");
return -EEXIST}
2. In file ./drivers/bus/pci/pci_common.cm function: pci_probe_all_drivers(=
), remove the following code:
/* Check if a driver is already loaded */ if (dev->driver !=3D NULL)
return -1;
However the substantial major changes are in each individual PMD probe call=
back when it is called several times with different devargs. For example it=
should not fail an already probed PCI device and just create new eth devic=
es for new representors.
> On the opposite, we could require rte_eal_hotplug_add() to try to add all
> matching devices, and fail if one is already probed.
>=20
> That's why a new parameter is added to specify if the function must fail =
or
> not when trying to add an already probed device.
>=20
Please note this new parameter ("fail_existing") will have to be propagated=
to all PMD probe callbacks.
Otherwise, in case (fail_existing =3D=3D false) a second call to rte_eal_ho=
tplug_add() will call the PMD probe callback, which may fail unless it is a=
ware of "fail_existing" parameter.
Alternatively "fail_existing" may be better named "enable_multi_probes".
Anyway - if the PMD probe() callback has to be updated to return a success/=
failure value (for more than one probe) - maybe we do not need a new parame=
ter and can rely on the PMD probe() callback the take the decision by retur=
ning success/failure value.
The counter part of rte_eal_hotplug_add() is rte_eal_hotplug_remove() which=
must be updated as well. For example when representors 1 and 2 exist - the=
n removing just representor 1 will have to make sure that the PCI device us=
ed for both representors is not unplugged since representor 2 is not remove=
d and it uses the same PCI device as representor 1.
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
> This patch contains only the change in the function itself as RFC.
>=20
> This idea was presented at Dublin during the "hotplug talk".
> ---
> lib/librte_eal/common/eal_common_dev.c | 4 +++-
> lib/librte_eal/common/include/rte_dev.h | 5 ++++-
> 2 files changed, 7 insertions(+), 2 deletions(-)
>=20
> diff --git a/lib/librte_eal/common/eal_common_dev.c
> b/lib/librte_eal/common/eal_common_dev.c
> index 678dbcac7..17d7e9089 100644
> --- a/lib/librte_eal/common/eal_common_dev.c
> +++ b/lib/librte_eal/common/eal_common_dev.c
> @@ -128,7 +128,7 @@ int rte_eal_dev_detach(struct rte_device *dev) }
>=20
> int __rte_experimental rte_eal_hotplug_add(const char *busname, const
> char *devname,
> - const char *devargs)
> + const char *devargs, bool fail_existing)
> {
> struct rte_bus *bus;
> struct rte_device *dev;
> @@ -173,6 +173,8 @@ int __rte_experimental rte_eal_hotplug_add(const
> char *busname, const char *devn
> }
>=20
> if (dev->driver !=3D NULL) {
> + if (!fail_existing)
> + return 0;
> RTE_LOG(ERR, EAL, "Device is already plugged\n");
> return -EEXIST;
> }
> diff --git a/lib/librte_eal/common/include/rte_dev.h
> b/lib/librte_eal/common/include/rte_dev.h
> index b80a80598..10a1cd2b4 100644
> --- a/lib/librte_eal/common/include/rte_dev.h
> +++ b/lib/librte_eal/common/include/rte_dev.h
> @@ -201,11 +201,14 @@ int rte_eal_dev_detach(struct rte_device *dev);
> * capable of handling it and pass it to the driver probing function.
> * @param devargs
> * Device arguments to be passed to the driver.
> + * @param fail_existing
> + * If true and a matching device is already probed, then return -EEXIS=
T.
> + * If false, then skip the already probed device without returning an =
error.
> * @return
> * 0 on success, negative on error.
> */
> int __rte_experimental rte_eal_hotplug_add(const char *busname, const
> char *devname,
> - const char *devargs);
> + const char *devargs, bool fail_existing);
>=20
> /**
> * @warning
> --
> 2.18.0