> -----Original Message----- > From: dev <[email protected]> On Behalf Of Ruifeng Wang > Sent: Thursday, September 16, 2021 6:17 PM > To: Jerin Jacob <[email protected]>; David Christensen > <[email protected]> > Cc: Bruce Richardson <[email protected]>; dpdk-dev > <[email protected]>; Luca Boccassi <[email protected]>; David Marchand > <[email protected]>; [email protected]; Ilya Maximets > <[email protected]>; [email protected]; Honnappa Nagarahalli > <[email protected]>; Ananyev, Konstantin > <[email protected]>; Ferruh Yigit <[email protected]>; nd > <[email protected]> > Subject: Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch > flag > > > -----Original Message----- > > From: Jerin Jacob <[email protected]> > > Sent: Thursday, September 16, 2021 11:43 AM > > To: David Christensen <[email protected]> > > Cc: Bruce Richardson <[email protected]>; dpdk-dev > > <[email protected]>; Luca Boccassi <[email protected]>; David Marchand > > <[email protected]>; [email protected]; Ilya Maximets > > <[email protected]>; [email protected]; Ruifeng Wang > > <[email protected]>; Honnappa Nagarahalli > > <[email protected]>; Ananyev, Konstantin > > <[email protected]>; Ferruh Yigit <[email protected]> > > Subject: Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine > > arch flag > > > > On Thu, Sep 16, 2021 at 2:53 AM David Christensen > > <[email protected]> > > wrote: > > > > > > > > > > > > On 9/15/21 9:28 AM, Bruce Richardson wrote: > > > > On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote: > > > >> Traditionally any apps built using DPDK had to support the same > > > >> instruction sets as supported when the DPDK SDK itself was built, > > > >> since that was "leaked" through to the end-app and DPDK headers > > > >> via > > > >> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over > to > > > >> meson for app build correctness the "-march=" flag was included > > > >> in the pkg-config cflags output. > > > >> > > > >> However, since the DPDK-specific CPU flags are now obsolete, and > > > >> we instead check directly for compiler-defined flags, we should > > > >> no longer need to force the exact same architecture match in all > > > >> cases. To faciliate such flexibility, a new > > > >> pkg_config_machine_args array - which defaults to the existing > > > >> machine_args array has been defined. The individual architectures > > > >> - x86, arm and ppc - can choose if and how to override this value > themselves. > > > >> > > > >> For x86, since SSE4.2 is the minimum instruction-set level needed > > > >> to run DPDK, and since some header files assume that minimum > > > >> level of instruction set support, we override the "-march=" value > > > >> with "- > > msse4" > > > >> for the pkg-config file. This allows end applications to set > > > >> their own "march" value while still ensuring valid DPDK compilation. > > > >> > > > >> Signed-off-by: Bruce Richardson <[email protected]> > > > >> --- > > > >> > > > >> CC: Jerin Jacob <[email protected]> > > > >> CC: Ruifeng Wang <[email protected]> > > > >> CC: Honnappa Nagarahalli <[email protected]> > > > >> CC: David Christensen <[email protected]> for Feedback > > > >> requested from ARM and PPC maintainers as to this change and what > > > >> flags, if any, need to be in the .pc file for DPDK on such > > > >> platforms. For example - is setting 'pkg_config_machine_args' to > > > >> 'machine_args' by default necessary behaviour? > > > >> > > > > > > > > Ping for further thoughts or input on this patch. > > > > Armv8 has dedicated config(taken least cpu flags which supports all > > armv8) for this purpose config/arm/arm64_armv8_linux_gcc. > > So this change looks good to me. @Ruifeng Wang (Arm Technology China) > > Any comments? > > > > Agree. For distro build, only armv8-a is requested. The change looks fine.
This is fine if "cross-file" is provided when doing distro build. However, when "-Dmachine=default"/"-Dplatform=default" is used instead of "cross-file" to do distro build, current change in config/meson.build will lead to " pkg_config_machine_args = -march=generic". This is because generic build is handled by subsequent arch specific config on Arm. I think moving the change in config/meson.build down below line #307 subdir(arch_subdir) will address aforementioned issue. As by the time, machine_args has been updated with proper value. > > Thanks, > Ruifeng > > > > > > > > On initial inspection I don't see any additional value for PPC systems. > > > Selection of a CPU through -mcpu implies a full ISA for that CPU, > > > including things like vector extensions, at least with respect to > > > the minimum supported POWER8 CPU (ISA 2.07) and later ISAs. The > > > values of machine_args and pkg_config_machine_args should be > > > identical in all cases I can think of. > > > > > > If a third party OpenPOWER CPU comes along some time in the future > > > then the requirements may change. > > > > > > > > > > > > > > Dave
