Re: [dpdk-dev] [PATCH v2] net/mlx5: add support for 32bit systems

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/5/2018 11:09 AM, Mordechay Haimovsky wrote:
> Hi,
>  Didn’t see it in our setups (not an excuse),  Investigating ....

Thanks. Perhaps it can be related to compiler version:
gcc (GCC) 8.1.1 20180502 (Red Hat 8.1.1-1)
(ICC 32bit also gave same build error.)

btw, to clarify rdma-core v19 build errors was not just for 32bit build, I lost
my log but I can reproduce if you require.

> 
> Moti
> 
>> -----Original Message-----
>> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
>> Sent: Wednesday, July 4, 2018 4:49 PM
>> To: Mordechay Haimovsky <motih@mellanox.com>; Shahaf Shuler
>> <shahafs@mellanox.com>
>> Cc: Adrien Mazarguil <adrien.mazarguil@6wind.com>; dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH v2] net/mlx5: add support for 32bit systems
>>
>> On 7/2/2018 12:11 PM, Moti Haimovsky wrote:
>>> This patch adds support for building and running mlx5 PMD on 32bit
>>> systems such as i686.
>>>
>>> The main issue to tackle was handling the 32bit access to the UAR as
>>> quoted from the mlx5 PRM:
>>> QP and CQ DoorBells require 64-bit writes. For best performance, it is
>>> recommended to execute the QP/CQ DoorBell as a single 64-bit write
>>> operation. For platforms that do not support 64 bit writes, it is
>>> possible to issue the 64 bits DoorBells through two consecutive
>>> writes, each write 32 bits, as described below:
>>> * The order of writing each of the Dwords is from lower to upper
>>>   addresses.
>>> * No other DoorBell can be rung (or even start ringing) in the midst of
>>>   an on-going write of a DoorBell over a given UAR page.
>>> The last rule implies that in a multi-threaded environment, the access
>>> to a UAR page (which can be accessible by all threads in the process)
>>> must be synchronized (for example, using a semaphore) unless an atomic
>>> write of 64 bits in a single bus operation is guaranteed. Such a
>>> synchronization is not required for when ringing DoorBells on
>>> different UAR pages.
>>>
>>> Signed-off-by: Moti Haimovsky <motih@mellanox.com>
>>> ---
>>> v2:
>>> * Fixed coding style issues.
>>> * Modified documentation according to review inputs.
>>> * Fixed merge conflicts.
>>> ---
>>>  doc/guides/nics/features/mlx5.ini |  1 +
>>>  doc/guides/nics/mlx5.rst          |  6 +++-
>>>  drivers/net/mlx5/mlx5.c           |  8 ++++-
>>>  drivers/net/mlx5/mlx5.h           |  5 +++
>>>  drivers/net/mlx5/mlx5_defs.h      | 18 ++++++++--
>>>  drivers/net/mlx5/mlx5_rxq.c       |  6 +++-
>>>  drivers/net/mlx5/mlx5_rxtx.c      | 22 +++++++------
>>>  drivers/net/mlx5/mlx5_rxtx.h      | 69
>> ++++++++++++++++++++++++++++++++++++++-
>>>  drivers/net/mlx5/mlx5_txq.c       | 13 +++++++-
>>>  9 files changed, 131 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/doc/guides/nics/features/mlx5.ini
>>> b/doc/guides/nics/features/mlx5.ini
>>> index e75b14b..b28b43e 100644
>>> --- a/doc/guides/nics/features/mlx5.ini
>>> +++ b/doc/guides/nics/features/mlx5.ini
>>> @@ -43,5 +43,6 @@ Multiprocess aware   = Y
>>>  Other kdrv           = Y
>>>  ARMv8                = Y
>>>  Power8               = Y
>>> +x86-32               = Y
>>>  x86-64               = Y
>>>  Usage doc            = Y
>>> diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index
>>> 7dd9c1c..5fbad60 100644
>>> --- a/doc/guides/nics/mlx5.rst
>>> +++ b/doc/guides/nics/mlx5.rst
>>> @@ -49,7 +49,7 @@ libibverbs.
>>>  Features
>>>  --------
>>>
>>> -- Multi arch support: x86_64, POWER8, ARMv8.
>>> +- Multi arch support: x86_64, POWER8, ARMv8, i686.
>>>  - Multiple TX and RX queues.
>>>  - Support for scattered TX and RX frames.
>>>  - IPv4, IPv6, TCPv4, TCPv6, UDPv4 and UDPv6 RSS on any number of
>> queues.
>>> @@ -477,6 +477,10 @@ RMDA Core with Linux Kernel
>>>  - Minimal kernel version : v4.14 or the most recent 4.14-rc (see
>>> `Linux installation documentation`_)
>>>  - Minimal rdma-core version: v15+ commit 0c5f5765213a ("Merge pull
>> request #227 from yishaih/tm")
>>>    (see `RDMA Core installation documentation`_)
>>> +- When building for i686 use:
>>> +
>>> +  - rdma-core version 18.0 or above built with 32bit support.
>>
>> related "or above" part, v19 giving build errors with mlx5, FYI.
>>
>> And with v18 getting build errors originated from rdma headers [1], am I
>> doing something wrong?
>>
>> [1]
>> In file included from .../dpdk/drivers/net/mlx5/mlx5_glue.c:20:
>> .../rdma-core/build32/include/infiniband/mlx5dv.h: In function
>> ‘mlx5dv_x86_set_data_seg’:
>> .../rdma-core/build32/include/infiniband/mlx5dv.h:787:69: error: right shift
>> count >= width of type [-Werror=shift-count-overflow]
>>   __m128i val  = _mm_set_epi32((uint32_t)address, (uint32_t)(address >>
>> 32), lkey, length);
>>                                                                      ^~