Date:   Mon, 30 Jan 2017 12:00:24 -0800
From:   Tom Herbert <tom@...bertland.com>
To:     Saeed Mahameed <saeedm@....mellanox.co.il>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net-next 0/4] mlx5: Create build configuration options

On Sun, Jan 29, 2017 at 12:07 AM, Saeed Mahameed
<saeedm@....mellanox.co.il> wrote:
> On Sat, Jan 28, 2017 at 7:19 PM, Tom Herbert <tom@...bertland.com> wrote:
>> On Sat, Jan 28, 2017 at 3:38 AM, Saeed Mahameed
>> <saeedm@....mellanox.co.il> wrote:
>>> On Fri, Jan 27, 2017 at 8:13 PM, Tom Herbert <tom@...bertland.com> wrote:
>>>> On Fri, Jan 27, 2017 at 9:58 AM, Saeed Mahameed
>>>> <saeedm@....mellanox.co.il> wrote:
>>>>> On Fri, Jan 27, 2017 at 1:32 AM, Tom Herbert <tom@...bertland.com> wrote:
>>>>>> This patchset creates configuration options for sriov, vxlan, eswitch,
>>>>>> and tc features in the mlx5 driver. The purpose of this is to allow not
>>>>>> building these features. These features are optional advanced features
>>>>>> that are not required for a core Ethernet driver. A user can disable
>>>>>> these features which resuces the amount of code in the driver. Disabling
>>>>>> these features (and DCB) reduces the size of mlx5_core.o by about 16%.
>>>>>> This is also can reduce the complexity of backport and rebases since
>>>>>> user would no longer need to worry about dependencies with the rest of
>>>>>> the kernel that features which might not be of any interest to a user
>>>>>> may bring in.
>>>>>>
>>>>>> Tested: Build and ran the driver with all features enabled (the default)
>>>>>> and with none enabled (including DCB). Did not see any issues. I did
>>>>>> not explicity test operation of ayy of features in the list.
>>>>>>
>>>>>
>>>>> Basically I am not against this kind of change, infact i am with it,
>>>>> although I would have done some restructuring in the driver before i
>>>>> did such change ;), filling the code with ifdefs is not a neat thing.
>>>>>
>>>> If you wish, please take this as an RFC and feel free to structure the
>>>> code the right way. I think the intent is clear enough and looks like
>>>> davem isn't going to allow the directory restructuring so something
>>>> like this seems to be the best course of action now.
>>>>
>>>
>>> Right.
>>>
>>>>> I agree this will simplify backporting and provide some kind of
>>>>> feature separation inside the driver.
>>>>> But this will also increase the testing matrix we need to cover and
>>>>> increase the likelihood of kbuild breaks by an order of magnitude.
>>>>>
>>>> The testing matrix already exploded with the proliferation of
>>>> supported features. If anything this reduces the test matrix problem.
>>>> For instance, if we make a change to the core driver and functionality
>>>> properly isolated there is a much better chance that this won't affect
>>>> peripheral functionality and vice versa. It is just not feasible for
>>>> us to test every combination of NIC features for every change being
>>>> made.
>>>>
>>>
>>> Yes for isolated features, but for base functionality, we need to test
>>> it with all new device specific kconfig combinations on every patch!
>>
>> Sorry, but that is the price you need to pay for a feature rich device.
>>
>> On the subject of testing, I don't really see any indication in these
>> patches on how patches are being tested. Also, there are patches that
>> fix things without any mention of how to repro the problems. It is
>
> I Will do my best to provide more information in fixes commit
> messages, Thanks for the input.
>
>> critical that we know IPv6 is tested as much or more than IPv4 (just
>
> For the record, for every IPv4 test in our automatic regression system
> we have an IPv6 equivalent test,
> not to mention IPv6-only directed tests.
>
Great to know. Is there a publicly available description of what
specific tests are in the suite?

>> last week with hit yet another IPv6-only issue in an another upstream
>> driver that should have been caught with a simple load test-- this
>
> Is there any IPv6-only functionality issues with mlx4/mlx5 that we
> don't know about ?
> If you do see any of those, please report them so we take the needed
> corrective actions to fix them and cover them in our regression.
>
If we see them we will certainly let you know. This is not just
functionality either, performance regression versus IPv4 should also
be considered serious issues.

>> really is not acceptable any more!). Please add a description of how
>> patches were tested to commit logs.
>>
>
> Acknowledge.
>

Thanks,
Tom

>> Tom
>>
>>> since a misplaced code inside or outside the correct ifdef
>>> can easily go unnoticed and break functionality.
>>>
>>>>> One more thing, do we really need a device specific flag per feature
>>>>> per vendor per device?  can't we just use the same kconfig flag for
>>>>> all drivers and if there is a more generic system wide flag that
>>>>> covers the same feature
>>>>> can't we just use it, for instance instead of
>>>>> CONFIG_<DRIVER_NAME>_SRIOV why not use already existing CONFIG_PCI_IOV
>>>>> for all drivers ?
>>>>>
>>>> That sounds good to me. We already have CONFIG_RFS_ACCEL and others
>>>> that do that.
>>>>
>>>> Tom
>>>>
>>>>> Saeed.
>>>>>
>>>>>>
>>>>>>
>>>>>> Tom Herbert (4):
>>>>>>   mlx5: Make building eswitch configurable
>>>>>>   mlx5: Make building SR-IOV configurable
>>>>>>   mlx5: Make building tc hardware offload configurable
>>>>>>   mlx5: Make building vxlan hardware offload configurable
>>>>>>
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/Kconfig   |  35 ++++++
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/Makefile  |  16 ++-
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 129 ++++++++++++++++------
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/en_tc.c   |  39 +++++--
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/eq.c      |   4 +-
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/lag.c     |   2 +
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/main.c    |  32 ++++--
>>>>>>  drivers/net/ethernet/mellanox/mlx5/core/sriov.c   |   6 +-
>>>>>>  8 files changed, 205 insertions(+), 58 deletions(-)
>>>>>>
>>>>>> --
>>>>>> 2.9.3
>>>>>>

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