-----Original Message-----

Date: Wed, 31 Jan 2018 11:57:10 +0000
From: Ophir Munk <redacted>
To: Jerin Jacob <redacted>
CC: "dev@dpdk.org" <redacted>, Thomas Monjalon <redacted>,
 Pascal Mazon [off-list ref], Jan Viktorin
 [off-list ref], Jianbo Liu [off-list ref]
Subject: RE: [dpdk-dev]  [PATCH] net/tap: fix build issue with ARM32

quoted

-----Original Message-----
From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
Sent: Wednesday, January 31, 2018 1:31 PM
To: Ophir Munk <redacted>
Cc: dev@dpdk.org; Thomas Monjalon <redacted>; Pascal
Mazon [off-list ref]; Jan Viktorin
[off-list ref]; Jianbo Liu [off-list ref]
Subject: Re: [dpdk-dev] [PATCH] net/tap: fix build issue with ARM32

-----Original Message-----

quoted

Date: Wed, 31 Jan 2018 10:38:32 +0000
From: Ophir Munk <redacted>
To: Jerin Jacob <redacted>
CC: "dev@dpdk.org" <redacted>, Thomas Monjalon
[off-list ref],  Pascal Mazon [off-list ref],

Jan

quoted

Viktorin  [off-list ref], Jianbo Liu [off-list ref]
Subject: RE: [dpdk-dev]  [PATCH] net/tap: fix build issue with ARM32

Hi,
Please see inline

quoted

-----Original Message-----
From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
Sent: Wednesday, January 31, 2018 12:24 PM
To: Ophir Munk <redacted>
Cc: dev@dpdk.org; Thomas Monjalon <redacted>; Pascal
Mazon [off-list ref]; Jan Viktorin
[off-list ref]; Jianbo Liu [off-list ref]
Subject: Re: [dpdk-dev] [PATCH] net/tap: fix build issue with ARM32

-----Original Message-----

quoted

Date: Wed, 31 Jan 2018 09:59:45 +0000
From: Ophir Munk <redacted>
To: Jerin Jacob <redacted>, "dev@dpdk.org"
 [off-list ref]
CC: Thomas Monjalon <redacted>, Pascal Mazon
[off-list ref], Jan Viktorin [off-list ref],
Jianbo  Liu [off-list ref]
Subject: RE: [dpdk-dev]  [PATCH] net/tap: fix build issue with
ARM32

Hi,
Please see comments inline

quoted

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jerin Jacob
Sent: Wednesday, January 31, 2018 7:14 AM
To: dev@dpdk.org
Cc: Thomas Monjalon <redacted>; Jerin Jacob
[off-list ref]; Pascal Mazon
[off-list ref]; Jan Viktorin
[off-list ref]; Jianbo Liu [off-list ref]
Subject: [dpdk-dev] [PATCH] net/tap: fix build issue with ARM32

arm32 Linux does not support eBPF interface.
Since tap PMD driver has a dependency on eBPF(the symbol
__NR_bpf), disabling it armv7 config.

compilation error log:
In file included from /tmp/dpdk/drivers/net/tap/tap_bpf_api.c:15:0:
/tmp/dpdk/drivers/net/tap/tap_bpf.h:103:4: error: #error
__NR_bpf not defined  #  error __NR_bpf not defined
    ^

arm architecture is missing is file drivers/tap/tap_bpf.h I
suggest adding it, for example

# elif defined(__arm__)
#  define __NR_bpf 386

By looking at Linux source code

https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fel

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ixi
r.free-

electrons.com%2Flinux%2Fv4.15%2Fsource%2Ftools%2Fbuild%2Ffeature%2

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Ftest-

bpf.c%23L6&data=02%7C01%7Cophirmu%40mellanox.com%7C19f50ad7f27

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34d00173808d56894c997%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%

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7C0%7C636529910613736017&sdata=ynsxHG9fvao4LyfWLo4GVJjlKNmcF0q

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0BkFocJyarAE%3D&reserved=0
I am not sure, Is eBPF support available for arm32 support?

TAP eBPF has a graceful approach: it must successfully compile on all
Linux distributions. If a specific kernel cannot support eBPF it will
gracefully refuse the eBPF netlink message sent to it.
Thus, there is no harm even if there is no eBPF support available for arm32.

OK. But, To enable grace full refuse, we should not any random system call
number like #define __NR_bpf 386.
It should at least unused for arm32.

For arm - system call 386 seems to be used only for eBPF
http://elixir.free-electrons.com/linux/v4.15/source/arch/arm64/include/asm/unistd32.h#L796

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You should enable TAP compilation for cases where you only need TAP

without eBPF.

Yes. It would have been better if new eBPF depended features would have
under conditional compilation flag so it it can be turned off selectively.

I am in favor of keeping configuration as simple as possible if possible.
I will issue a PR which includes arm BPF definition

OK.

Looks like systemd is using the similar method.
https://github.com/systemd/systemd/blob/master/src/basic/missing_syscall.h#L334