Re: [ovs-dev] [PATCH v1 4/4] travis: Enable OVS Travis CI for arm

[Lance Yang (Arm Technology China)]

> -----Original Message-----
> From: Ilya Maximets <i.maxim...@ovn.org>
> Sent: Tuesday, November 26, 2019 8:48 PM
> To: Ilya Maximets <i.maxim...@ovn.org>; Lance Yang (Arm Technology China)
> <lance.y...@arm.com>; ovs-dev@openvswitch.org
> Cc: Jieqiang Wang (Arm Technology China) <jieqiang.w...@arm.com>; Gavin Hu 
> (Arm
> Technology China) <gavin...@arm.com>; Jingzhao Ni (Arm Technology China)
> <jingzhao...@arm.com>; dwil...@us.ibm.com; nd <n...@arm.com>; Ruifeng Wang 
> (Arm
> Technology China) <ruifeng.w...@arm.com>; Yanqin Wei (Arm Technology China)
> <yanqin....@arm.com>; Ben Pfaff <b...@ovn.org>
> Subject: Re: [ovs-dev] [PATCH v1 4/4] travis: Enable OVS Travis CI for arm
>
> On 26.11.2019 13:37, Ilya Maximets wrote:
> > On 25.11.2019 7:28, Lance Yang (Arm Technology China) wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: Ilya Maximets <i.maxim...@ovn.org>
> >>> Sent: Friday, November 22, 2019 6:36 PM
> >>> To: Lance Yang (Arm Technology China) <lance.y...@arm.com>; Ilya
> >>> Maximets <i.maxim...@ovn.org>; ovs-dev@openvswitch.org
> >>> Cc: Jieqiang Wang (Arm Technology China) <jieqiang.w...@arm.com>;
> >>> Gavin Hu (Arm Technology China) <gavin...@arm.com>; Jingzhao Ni (Arm
> >>> Technology China) <jingzhao...@arm.com>; dwil...@us.ibm.com; nd
> >>> <n...@arm.com>; Ruifeng Wang (Arm Technology China)
> >>> <ruifeng.w...@arm.com>; Yanqin Wei (Arm Technology China)
> >>> <yanqin....@arm.com>
> >>> Subject: Re: [ovs-dev] [PATCH v1 4/4] travis: Enable OVS Travis CI
> >>> for arm
> >>>
> >>> On 22.11.2019 10:35, Lance Yang (Arm Technology China) wrote:
> >>>> Hi Ilya,
> >>>>
> >>>> Thanks for your reply. Please see the inline reply.
> >>>>
> >>>> Best regards,
> >>>> Lance Yang
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Ilya Maximets <i.maxim...@ovn.org>
> >>>>> Sent: Friday, November 22, 2019 3:47 AM
> >>>>> To: Lance Yang (Arm Technology China) <lance.y...@arm.com>; ovs-
> >>>>> d...@openvswitch.org
> >>>>> Cc: Jieqiang Wang (Arm Technology China) <jieqiang.w...@arm.com>;
> >>>>> Gavin Hu (Arm Technology China) <gavin...@arm.com>; Jingzhao Ni
> >>>>> (Arm Technology China) <jingzhao...@arm.com>; dwil...@us.ibm.com;
> >>>>> nd <n...@arm.com>; Ruifeng Wang (Arm Technology China)
> >>>>> <ruifeng.w...@arm.com>
> >>>>> Subject: Re: [ovs-dev] [PATCH v1 4/4] travis: Enable OVS Travis CI
> >>>>> for arm
> >>>>>
> >>>>> On 20.11.2019 9:15, Lance Yang wrote:
> >>>>>> Enable part of travis jobs with gcc compiler for arm64
> >>>>>> architecture
> >>>>>>
> >>>>>> 1. Add arm jobs into the matrix in .travis.yml and define dpdk
> >>>>>> cache directory for arm64 architecture.
> >>>>>> 2. Temporarily disable sparse checker because of static code
> >>>>>> checking failure on arm64
> >>>>>
> >>>>> Could you provide the sparse error messages?
> >>>>> Maybe we could fix them instead of disabling.
> >>>>>
> >>>>>>
> >>>>>> Successful travis build jobs report:
> >>>>>> https://travis-ci.org/yzyuestc/ovs/builds/614299933
> >>>>>
> >>>>> There are some issues in Travis in above build.  It seems that
> >>>>> Travis fails to upload the resulted cache directory due to missing 
> >>>>> md5deep:
> >>>>>
> >>>>> ""
> >>>> [Lance]
> >>>> The issue occurred because sparse checker does not recognize some arm 
> >>>> neon
> intrinsics:
> >>>>
> >>>> 1. Some components in Open vSwitch source code directly includes
> >>>> the header file
> >>> <arm_neon.h>.
> >>>>
> >>>> 2. When compiling OvS with DPDK, OvS includes some DPDK headers,
> >>>> which sometimes includes <arm_neon.h>. You can see the details of
> >>>> the error in the report at:
> >>>> https://travis-ci.org/yzyuestc/ovs/jobs/615414391
> >>>> after line 2693
> >>>>
> >>>> For the first issue where OvS directly imported the arm_neon.h,  I
> >>>> can fix it in my patch set
> >>> v2. However, for the second issue that DPDK project has imported the
> >>> arm neon intrinsics, it seems that I am unable to fix this issue until 
> >>> DPDK solved it.
> >>>
> >>> Hi.
> >>>
> >>> Thanks for the information.
> >>> Could, you, please, check if the following patch fixes the issue:
> >>>     https://patchwork.ozlabs.org/patch/1199398/
> >>> ?
> >> [Lance]
> >> Thanks for your reply.
> >>
> >> I downloaded and applied the patch from patchwork. However, it seems that 
> >> the patch
> does not work as expected. I attached the original travis report link: 
> https://travis-
> ci.org/yzyuestc/ovs/jobs/616442657#L2692. You can check the error after line 
> 2692.
> >
> >
> > Thanks for checking.  I found the root cause.
> > The issue is that GCC has NEON vector types as compiler built-in types.
> > x86 vector types (e.g. __m128i) are typedefs of a normal types with a
> > special 'vector_size' attribute that sparse understands.  But it can
> > not understand special built-in types.  Note that clang defines NEON
> > vector types with 'vector_size' attribute inside arm_neon.h, so it's
> > unclear why GCC doesn't do the same.
> >
> > So, there are 3 options on how we can fix that:
> >
> > 1. Create special include/sparse/arm_neon.h  header and mock all the
> >    GCC built-ins for NEON support.  This doesn't look very hard, but
> >    could take some time.  I tried to re-define all the base types this
> >    way, but it requires something else and I need to look at exact
> >    arm_neon.h that is in use to understand what is missing. We, probably,
> >    will have to mock a bunch of NEON-specific built-in functions too.
> >    Not sure if it worth the efforts.
> >
> > 2. Add NEON support to sparse itself, i.e. allow it to understand GCC
> >    specific vector types and built-in functions.  That is the most
> >    clean solution, but requires development in a different project and
> >    it's unclear when this support will be integrated to upstream sparse.
> >
> > 3. Just disable sparse for ARM in our Travis for now.  The easiest
> >    solution that you've already implemented.  So, we, probably, should
> >    start from this.  One thing that I'm asking is to add more information
> >    why it was disabled in commit message and in a comment in the travis
> >    file.  You may use some parts of my investigation above.
>
> There is one more option is to use clang for ARM64 build instead of gcc.
> We're not using sparse for clang builds right now.  If we'll be lucky someday 
> to make sparse
> work with clang in our Travis environment, there should be no such big issues 
> with NEON,
> because clang doesn't use built-in types.
>
> Is it possible to build OVS with clang on aarch64 in Travis?
>
> Best regards, Ilya Maximets.
[Lance]

Hi Ilya,

Thanks for the options you provided.

We will enable clang jobs on aarch64 in the next step. As a short-term 
solution, we prefer the third option to temporarily disable sparse running arm 
jobs. Meanwhile, we can wait for the sparse supports on neon.

Best regards,
Lance


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