[PATCH v4 1/2] config: correct cpu instruction set for cross build

[Joyce Kong]

> -----Original Message-----
> From: Stephen Hemminger <stephen at networkplumber.org>
> Sent: Friday, December 8, 2023 6:41 AM
> To: Joyce Kong <Joyce.Kong at arm.com>
> Cc: thomas at monjalon.net; Ruifeng Wang <Ruifeng.Wang at arm.com>;
> bruce.richardson at intel.com; dev at dpdk.org; nd <nd at arm.com>;
> stable at dpdk.org
> Subject: Re: [PATCH v4 1/2] config: correct cpu instruction set for cross build
> 
> On Tue,  5 Dec 2023 03:52:58 +0000
> Joyce Kong <joyce.kong at arm.com> wrote:
> 
> > The platform value would be 'native' only when not cross build.
> > Move the operation about modifying cpu_instruction_set while platform
> > equals 'native' to the not cross build branch.
> >
> > Fixes: bf66003b51ec ("build: use platform for generic and native
> > builds")
> > Cc: stable at dpdk.org
> >
> > Signed-off-by: Joyce Kong <joyce.kong at arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
> 
> Looks right, what is the impact on existing users doing current cross builds?

The original operation changes cpu_instruction_set to 'native' when both 'platform == native' and 'cpu_instruction_set == auto'.
There was no impact on the existing users for current cross build, as the cross files set cpu field to a specific arch, such as 'armv8-a', and this didn't trigger the modification for cpu_instruction_set.
However, if we want to use a common arch in cross files like 'auto', the modification operation would override 'native' value to cpu_instruction_set and b7676fcccab4 ("config: verify machine arch flag") would break the build as it tries to test -march=native.

> 
> Acked-by: Stephen Hemminger <stephen at networkplumber.org>