[meta-intel] [meta-dpdk][PATCH] dpdk: workaround sse mismatch error

[Anuj Mittal]

Hi Hongxu

On 10/11/2018 11:01 AM, Hongxu Jia wrote:
> On 2018年10月11日 08:21, Anuj Mittal wrote:

>> Is it possible that the value of -march is also being defined from
>> somewhere within dpdk leading to a mismatch?
> 
> Hi Anuj,
> 
> I think so, since var-DPDK_TARGET_MACHINE is `default' which mismatch
> with `-march=**' in var-HOST_CC_ARCH
> 
> For qemux86-64, while var-DPDK_TARGET_MACHINE is `default', its 
> `-march=corei7',
> it mismatch with `-march=core2' in var-HOST_CC_ARCH
> 
> [grep corei -rn mk]
> mk/machine/native/rte.vars.mk:35:# so, set the compilation target to be 
> a corei7, minimum target with SSE4.2.
> mk/machine/native/rte.vars.mk:38:    MACHINE_CFLAGS = -march=corei7
> mk/machine/default/rte.vars.mk:30:MACHINE_CFLAGS += -march=corei7
> mk/machine/wsm/rte.vars.mk:30:MACHINE_CFLAGS = -march=corei7 -maes -mpclmul
> mk/machine/snb/rte.vars.mk:30:MACHINE_CFLAGS = -march=corei7-avx
> mk/machine/nhm/rte.vars.mk:30:MACHINE_CFLAGS = -march=corei
> [grep corei -rn mk]
> 
> For default, its MACHINE_CFLAGS is ` -march=corei7', and set 
> `DPDK_TARGET_MACHINE = 'corei5''
> does not work, no mk/machine/corei5/rte.vars.mk to support it
> 
> I think this fix is not appropriate, please drop it. My suggestion is remove
> var-HOST_CC_ARCH from do_compile, V2 incoming
> 

I think we shouldn't be building with -march=corei7 (which is what it
will do if you remove HOST_CC_ARCH) if the underlying hardware doesn't
support it. It probably wouldn't even work since default value is
core2duo for qemu in tune-core2.inc which doesn't support SSE 4.2 (which
is a requirement for dpdk).

In my opinion, we should keep HOST_CC_ARCH and anyone using dpdk should
make sure that they define COMPATIBLE_MACHINE and DPDK_TARGET_MACHINE
properly depending on the arch that they are building for. Does that
make sense?

Thanks,

Anuj