Re: [dpdk-dev] [RFC PATCH v1] build: kni gcc cross-compilation support

-----Original Message-----
From: Bruce Richardson <redacted>
Sent: Friday, January 29, 2021 4:40 PM
To: Juraj Linkeš <redacted>
Cc: thomas@monjalon.net; Ruifeng.Wang@arm.com; jerinjacobk@gmail.com;
hemant.agrawal@nxp.com; ferruh.yigit@intel.com; aboyer@pensando.io;
dev@dpdk.org
Subject: Re: [RFC PATCH v1] build: kni gcc cross-compilation support

On Fri, Jan 29, 2021 at 03:17:02PM +0000, Juraj Linkeš wrote:

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-----Original Message-----
From: Bruce Richardson <redacted>
Sent: Friday, January 29, 2021 4:01 PM
To: Juraj Linkeš <redacted>
Cc: thomas@monjalon.net; Ruifeng.Wang@arm.com;
jerinjacobk@gmail.com; hemant.agrawal@nxp.com;
ferruh.yigit@intel.com; aboyer@pensando.io; dev@dpdk.org
Subject: Re: [RFC PATCH v1] build: kni gcc cross-compilation support

On Fri, Jan 29, 2021 at 02:47:57PM +0000, Juraj Linkeš wrote:

quoted

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-----Original Message-----
From: Bruce Richardson <redacted>
Sent: Friday, January 29, 2021 3:42 PM
To: Juraj Linkeš <redacted>
Cc: thomas@monjalon.net; Ruifeng.Wang@arm.com;
jerinjacobk@gmail.com; hemant.agrawal@nxp.com;
ferruh.yigit@intel.com; aboyer@pensando.io; dev@dpdk.org
Subject: Re: [RFC PATCH v1] build: kni gcc cross-compilation
support

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Can we find some way of getting it working for both cases.
For native builds we want:

* build kernel-dir = /lib/modules/<ver>/build
* install dir = /lib/modules/<ver>/extra/dpdk

What are the expected equivalent paths for cross building?

The ubuntu1804 packages are installing aarch64 cross files to
/usr/aarch64-

linux-gnu, so we could install it to /usr/aarch64-linux-
gnu/lib/modules/<ver>/extra/dpdk, or
/usr/<cross_triple>/lib/modules/<ver>/extra/dpdk in general. I
think we can get <ver> from 'make kernelversion', so that would
work, although I'm not sure this is the right place.

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So what do you specify as the "kernel_dir" for the cross compile?

The place where I cloned (and cross-compiled) linux sources: $HOME/linux.

So I think the key problem is that for cross-compilation you need
two completely independent paths, while for native builds the two can be

linked. Is that correct?

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Assuming that we want to install cross modules, then yes, although
it's incomplete. There's also the scenario when a user would use
different kernel_dir than the default for native builds. I don't know
why anyone would do that, but it is a theoretical possibility :-)

In the cross-compile install case, is the prefix /usr/aarch64-linux-gnu/ coming
from a DESTDIR environment variable? If it is, then we could just use the
kernel_dir option for the build path, and always install to /lib/modules/<ver>/...
allowing any cross-compiler relocation to take care of the rest.

It's not coming from anywhere. What I meant is that an ubuntu package such as 'libatomic1-arm64-cross' installs its headers/libs under /usr/aarch64-linux-gnu/.