Re: [dpdk-dev] [PATCH v5] build: kni cross-compilation support

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Tuesday, February 9, 2021 12:51 PM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: thomas@monjalon.net; Ruifeng.Wang@arm.com;
> Honnappa.Nagarahalli@arm.com; jerinjacobk@gmail.com;
> hemant.agrawal@nxp.com; ferruh.yigit@intel.com; aboyer@pensando.io;
> dev@dpdk.org
> Subject: Re: [PATCH v5] build: kni cross-compilation support
> 
> On Tue, Feb 09, 2021 at 09:47:05AM +0100, Juraj Linkeš wrote:
> > The kni linux module is using a custom target for building, which
> > doesn't take into account any cross compilation arguments. The
> > arguments in question are ARCH, CROSS_COMPILE (for gcc, clang) and CC,
> > LD (for clang). Get those from the cross file and pass them to the
> > custom target.
> >
> > The user supplied path may not contain the 'build' directory, such as
> > when using cross-compiled headers, so only append that in the default
> > case (when no path is supplied in native builds) and use the
> > unmodified path from the user otherwise. Also modify the install path
> accordingly.
> >
> > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> 
> Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>
> 
> Couple of small comments inline below.
> 
> > ---
> >  kernel/linux/kni/meson.build |  8 +--
> >  kernel/linux/meson.build     | 94 +++++++++++++++++++++++++++++++-----
> >  meson_options.txt            |  2 +-
> >  3 files changed, 86 insertions(+), 18 deletions(-)
> >
> > diff --git a/kernel/linux/kni/meson.build
> > b/kernel/linux/kni/meson.build index 07e0c9dae7..46b71c7418 100644
> > --- a/kernel/linux/kni/meson.build
> > +++ b/kernel/linux/kni/meson.build
> > @@ -13,7 +13,7 @@ kni_sources = files(  custom_target('rte_kni',
> >  	input: kni_sources,
> >  	output: 'rte_kni.ko',
> > -	command: ['make', '-j4', '-C', kernel_dir + '/build',
> > +	command: ['make', '-j4', '-C', kernel_build_dir,
> >  		'M=' + meson.current_build_dir(),
> >  		'src=' + meson.current_source_dir(),
> >  		'MODULE_CFLAGS=-include ' + meson.source_root() +
> > '/config/rte_config.h' + @@ -21,8 +21,8 @@ custom_target('rte_kni',
> >  		' -I' + meson.source_root() + '/lib/librte_kni' +
> >  		' -I' + meson.build_root() +
> >  		' -I' + meson.current_source_dir(),
> > -		'modules'],
> > +		'modules'] + cross_args,
> >  	depends: kni_mkfile,
> > -	install: true,
> > -	install_dir: kernel_dir + '/extra/dpdk',
> > +	install: install,
> > +	install_dir: kernel_install_dir,
> >  	build_by_default: get_option('enable_kmods')) diff --git
> > a/kernel/linux/meson.build b/kernel/linux/meson.build index
> > 5c864a4653..67c1cbd7e0 100644
> > --- a/kernel/linux/meson.build
> > +++ b/kernel/linux/meson.build
> > @@ -3,25 +3,93 @@
> >
> >  subdirs = ['kni']
> >
> > -# if we are cross-compiling we need kernel_dir specified -if
> > get_option('kernel_dir') == '' and meson.is_cross_build()
> > -	error('Need "kernel_dir" option for kmod compilation when cross-
> compiling')
> > -endif
> > +kernel_build_dir = get_option('kernel_dir') kernel_install_dir = ''
> > +install = not meson.is_cross_build()
> > +cross_args = []
> >
> > -kernel_dir = get_option('kernel_dir') -if kernel_dir == ''
> > -	# use default path for native builds
> > +if not meson.is_cross_build()
> > +	# native build
> >  	kernel_version = run_command('uname', '-r').stdout().strip()
> > -	kernel_dir = '/lib/modules/' + kernel_version
> > +	kernel_install_dir = '/lib/modules/' + kernel_version + '/extra/dpdk'
> > +	if kernel_build_dir == ''
> > +		# use default path for native builds
> > +		kernel_build_dir = '/lib/modules/' + kernel_version + '/build'
> > +	endif
> > +
> > +	# test running make in kernel directory, using "make kernelversion"
> > +	make_returncode = run_command('make', '-sC', kernel_build_dir,
> > +			'kernelversion').returncode()
> > +	if make_returncode != 0
> > +		# backwards compatibility:
> > +		# the headers could still be in the 'build' subdir
> > +		if not kernel_build_dir.endswith('build') and not
> kernel_build_dir.endswith('build/')
> > +			kernel_build_dir = join_paths(kernel_build_dir, 'build')
> > +			make_returncode = run_command('make', '-sC',
> kernel_build_dir,
> > +					'kernelversion').returncode()
> > +			if make_returncode == 0
> > +				warning('Deprecation notice: Specifying
> kernel_dir ' +
> > +					'without the build dir will be deprecated
> in the future.')
> > +			endif
> 
> I don't really think we need to deprecate this, since this should adequately
> support both options. Therefore, I suggest just dropping these last 4 lines and
> accepting both options.
> 

Ok, I'll remove the lines.

> > +		endif
> > +	endif
> > +
> > +	if make_returncode != 0
> > +		error('Cannot compile kernel modules as requested - are kernel
> headers installed?')
> > +	endif
> > +
> > +	# DO ACTUAL MODULE BUILDING
> > +	foreach d:subdirs
> > +		subdir(d)
> > +	endforeach
> > +
> > +	subdir_done()
> >  endif
> >
> > -# test running make in kernel directory, using "make kernelversion"
> > -make_returncode = run_command('make', '-sC', kernel_dir + '/build',
> > -		'kernelversion').returncode()
> > -if make_returncode != 0
> > -	error('Cannot compile kernel modules as requested - are kernel headers
> installed?')
> > +# cross build
> > +# if we are cross-compiling we need kernel_build_dir specified if
> > +kernel_build_dir == ''
> > +	error('Need "kernel_dir" option for kmod compilation when
> > +cross-compiling') endif cross_compiler = find_program('c').path() if
> > +cross_compiler.endswith('gcc')
> > +	cross_prefix = run_command([py3, '-c', 'print("' + cross_compiler +
> > +'"[:-3])']).stdout().strip() elif cross_compiler.endswith('clang')
> > +	cross_prefix = ''
> > +	found_target = false
> > +	# search for '-target' and use the arg that follows
> > +	# (i.e. the value of '-target') as cross_prefix
> > +	foreach cross_c_arg : meson.get_cross_property('c_args')
> > +		if found_target and cross_prefix == ''
> > +			cross_prefix = cross_c_arg
> > +		endif
> > +		if cross_c_arg == '-target'
> > +			found_target = true
> > +		endif
> > +	endforeach
> > +	if cross_prefix == ''
> > +		error('Didn\'t find -target and its value in' +
> > +		      ' c_args in input cross-file.')
> > +	endif
> > +	linker = 'lld'
> > +	foreach cross_c_link_arg : meson.get_cross_property('c_link_args')
> > +		if cross_c_link_arg.startswith('-fuse-ld')
> > +			linker = cross_c_link_arg.split('=')[1]
> > +		endif
> > +	endforeach
> > +	cross_args += ['CC=@0@'.format(cross_compiler),
> > +'LD=ld.@0@'.format(linker)] else
> > +	error('Unsupported cross compiler: @0@'.format(cross_compiler))
> >  endif
> >
> > +cross_arch = host_machine.cpu_family() if host_machine.cpu_family()
> > +== 'aarch64'
> > +	cross_arch = 'arm64'
> > +endif
> > +
> > +cross_args += ['ARCH=@0@'.format(cross_arch),
> > +	'CROSS_COMPILE=@0@'.format(cross_prefix)]
> > +
> >  # DO ACTUAL MODULE BUILDING
> >  foreach d:subdirs
> >  	subdir(d)
> > diff --git a/meson_options.txt b/meson_options.txt index
> > 6eff62e47d..de44d17c02 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -19,7 +19,7 @@ option('ibverbs_link', type: 'combo', choices :
> > ['static', 'shared', 'dlopen'],  option('include_subdir_arch', type: 'string', value:
> '',
> >  	description: 'subdirectory where to install arch-dependent headers')
> > option('kernel_dir', type: 'string', value: '',
> > -	description: 'Path to the kernel for building kernel modules. Headers
> must be in $kernel_dir/build. Modules will be installed in
> $DEST_DIR/$kernel_dir/extra/dpdk.')
> > +	description: 'Path to the kernel for building kernel modules.
> > +Headers must be in $kernel_dir. Modules will be installed in
> > +/lib/modules/$(uname -r)/extra/dpdk for native builds.')
> 
> While correct, the last sentence isn't really relevant to the build option, it's more
> an additional note, and it seems a bit awkward. Maybe it can be shortened by
> referencing "/lib/modules" rather than giving the full path.
> Alternatively, maybe just putting the details in the documentation is a better
> plan, and leaving the comment here as just "path to the kernel for building
> kernel modules".
> 

Having it in docs would be better, but where exactly? I tried looking, but didn't find a suitable place.

> >  option('machine', type: 'string', value: 'native',
> >  	description: 'set the target machine type')  option('max_ethports',
> > type: 'integer', value: 32,
> > --
> > 2.20.1
> >