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 <bruce.richard...@intel.com>
---
CC: Jerin Jacob <jer...@marvell.com>
CC: Ruifeng Wang <ruifeng.w...@arm.com>
CC: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
CC: David Christensen <d...@linux.vnet.ibm.com> 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.
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
