[dpdk-dev] [PATCH 0/9] rte_bus parse API

[Jan Blunck]

On Wed, Jun 7, 2017 at 9:55 PM, Gaëtan Rivet <gaetan.rivet at 6wind.com> wrote:
> On Wed, Jun 07, 2017 at 07:22:05PM +0200, Jan Blunck wrote:
>> On Wed, May 24, 2017 at 5:12 PM, Gaetan Rivet <gaetan.rivet at 6wind.com> wrote:
>> > Following the evolutions announced in [1], here is the first part of
>> > the rte_devargs rework planned for 17.08. The rationale has been partially
>> > explained in [2].
>> >
>> > This first part covers the introduction of the necessary facilities in
>> > rte_bus to allow for generic device parsing. This API is implemented for
>> > the virtual and PCI buses. Additionally, this rte_bus evolution is being
>> > used within rte_devargs to characterize a device type by its bus.
>> > This work is the first of two parts to reduce the dependency of the EAL
>> > upon specific bus implementations.
>> >
>> > Two public functions are added to rte_bus to help bus recognition:
>> >
>> > - rte_bus_from_name
>> > - rte_bus_from_dev
>> >
>> > These functions are made public because the bus handle within devargs
>> > becomes the generic device type. Recognizing device types is useful for
>> > buses and PMDs alike.
>> > The modified rte_devargs parsing allows declaring on the EAL command line
>> > explicit buses to handle a device. The format is as follow:
>> >
>> >   --vdev="virtual:net_ring0" --vdev="net_tap0,iface=tap0"
>> >   -w PCI:00:02.0 -w 00:03.0
>> >
>>
>> I don't see the point of doing this. The --vdev parameter implicitly
>> defines the bus by its name (--vdev aka virtual device).
>>
>> Why don't you add a commandline "--dev" parameter that supports a
>> "bus=" devarg? You would need to clarify what that means for other
>> busses than the virtual one. Is the bus switched into whitelist mode
>> by that?
>>
>>
>
> We cannot keep the current -w, -b and --vdev parameter. Those are
> processed by the EAL, and use specifics from the virtual and PCI buses.
>
> The rte_devargs rework has been to make the same functionality generic
> to all rte_bus. As seen quickly in [2], rte_devargs has two functions:
>
> * Validating a device declaration
> * Keeping the relevant device info until it has been processed.
>

I don't agree with the validation step. This is highly
device/driver/bus specific and I don't believe that just because you
have created a rte_devargs it is a guarantee that the device is valid.
Besides that it makes statically embedding rte_devargs into other
structures impossible. As I see it rte_devargs is a key-value list
with some keys that are generic. This would make application
development much easier.


> Both functionalities have been genericized. This results in all parameters
> being able to be used with all types of devices. This is inherent to the
> EAL becoming bus-agnostic.
>
> Now, it is absolutely possible to rename for example -w as --dev, as it
> is the expected behavior from users. This however should be discussed by
> the community, last time I talked about the possibility of switching the
> default of the PCI bus to whitelist mode the community wasn't all that
> enthused by the prospect.
>
> Finally, I do not like the idea of a special devarg just for declaring
> explicitly buses for devices. The bus is not a device modifier, nor is
> it a driver parameter. The bus is a way to define the location of the
> device on the system. Adding a special "bus=" devargs means having some
> preprocessing done on devargs upon rte_devargs allocation. This was
> already abused by the bonding PMD with the driver= parameter. I do not
> support this and did not want to repeat it. Passing down the device args
> is a simple process and we should keep it as simple as possible.
>
> I know you do not like having the bus as part of the device name.
> As a compromise, I made the current system flexible and allowed the legacy
> device definition to be kept.
>
> However with a purely generic process, it is necessary to at least offer
> the possibility to the user to explicitly use a bus, as nothing prevents
> conflicting device names from existing.
>
>> > [2]: http://dpdk.org/ml/archives/dev/2017-May/065670.html
>
>> > This explicit bus designation is optional; no evolution is currently
>> > forced on users to migrate to this new format. The separating character is
>> > arbitrary and can be any character illegal within a bus name.
>> > Subsequently, what is allowed within a bus name has been formally
>> > defined and is now enforced.
>> >
>> > [1]: http://dpdk.org/ml/archives/dev/2017-May/065634.html
>> > [2]: http://dpdk.org/ml/archives/dev/2017-May/065670.html
>> >
>> > This patchset depends on:
>> >
>> > bus: attach / detach API
>> > http://dpdk.org/ml/archives/dev/2017-May/066330.html
>> > http://dpdk.org/dev/patchwork/patch/24489/
>> >
>> > Gaetan Rivet (9):
>> >   bus: fix bus name registration
>> >   bus: verify bus name on registration
>> >   bus: introduce parsing functionality
>> >   vdev: implement parse bus operation
>> >   pci: implement parse bus operation
>> >   bus: add helper to find bus from a name
>> >   bus: add helper to find a bus from a device name
>> >   vdev: expose bus name
>> >   devargs: parse bus info
>> >
>> >  lib/librte_eal/bsdapp/eal/rte_eal_version.map   |  8 +++
>> >  lib/librte_eal/common/eal_common_bus.c          | 47 +++++++++++++++++
>> >  lib/librte_eal/common/eal_common_devargs.c      | 17 +++++-
>> >  lib/librte_eal/common/eal_common_pci.c          | 19 +++++++
>> >  lib/librte_eal/common/eal_common_vdev.c         | 70 ++++++++++++++-----------
>> >  lib/librte_eal/common/eal_private.h             | 16 ++++++
>> >  lib/librte_eal/common/include/rte_bus.h         | 49 ++++++++++++++++-
>> >  lib/librte_eal/common/include/rte_devargs.h     |  3 ++
>> >  lib/librte_eal/common/include/rte_vdev.h        |  2 +
>> >  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  8 +++
>> >  10 files changed, 205 insertions(+), 34 deletions(-)
>> >
>> > --
>> > 2.1.4
>> >
>
> --
> Gaėtan Rivet
> 6WIND