Re: [dpdk-dev] [PATCH v9 1/1] net/af_xdp: introduce AF XDP PMD driver

[Ye Xiaolong <xiaolong.ye@intel.com>]

On 04/03, Ferruh Yigit wrote:
[snip]
>
>It seems, 'tools/include/asm/barrier.h' is required for 'smp_wmb()' &
>'smp_rmb()' in 'xsk.h'.
>We have equivalents of these in DPDK [1], and perhaps it can be possible to use
>them and not include this header at all.
>
>in 'rte_eth_af_xdp.c', before including 'xsk.h', we can include an local
>compatibility header which does following should work:
>#define smp_rmb() rte_rmb()
>#define smp_wmb() rte_wmb()
>
>@Xiaolong, what do you think?

It sounds perfect to me, I'll take it in my next version.
Something to confirm, So we can now assume af_xdp pmd user would use kernel (say v5.1-rc4) 
that contains fixes regarding to xsk.h and libelf, I still need to do following
changes.

1. I shall use <bpf/xsk.h> as xsk.h should be installed in system folders.
2. `-lelf` is not needed in rte.app.mk
3. I need to document the libbpf build and install steps in af_xdp.rst
4. add the above two defines before including xsk.h

Thanks,
Xiaolong


>
>[1]
>https://git.dpdk.org/dpdk/tree/lib/librte_eal/common/include/arch/x86/rte_atomic.h?h=v19.02#n30
>
>> 
>> The one in tools/include also is GPL-2.0 only so it cannot be included
>> from the PMD, which is BSD-3-clause only (and it recursively includes
>> the other arch-specific kernel headers)
>> 
>>> Anyway, as Xiaolong mentioned, following is working, can it work from
>>> a distro
>>> point of view:
>>> - get kernel source code (>= v5.1-rc1)
>>> - build libbfp and install
>>> - set 'RTE_KERNELDIR' to point kernel source path
>>> - build dpdk with af_xdp enabled
>> 
>> As long as the full kernel tree is required, we cannot enable it in
>> Debian and Ubuntu - we can't have it at build time on the build
>> workers, and also there's the licensing problem.
>
>Got it.
>
>In above steps, 'libbpf' also build from kernel source tree, will it be problem
>in you builds to not have it build from source?
>
>If not, taking into account that xsk.h also will be fixed, only
>'tools/include/asm/barrier.h' remains the problem, and it looks like it can be
>solved, please check above.
>
>
>> 
>>>> Also, the license in asm/barrier.h is GPL-2.0 only. It is not a
>>>> userspace header so it is not covered by the userspace exception,
>>>> which
>>>> means at the very least the af_xdp PMD shared object is also
>>>> licensed
>>>> under GPL-2.0 only, isn't it?
>>>>
>>>
>>>
>