Re: [RFC][PATCH v3 1/5] sparc64: Fix asm/percpu.h build error

[David Miller]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Fri, 29 May 2020 23:35:51 +0200

> ../arch/sparc/include/asm/percpu_64.h:7:24: warning: call-clobbered register used for global register variable
> register unsigned long __local_per_cpu_offset asm("g5");

The "-ffixed-g5" option on the command line tells gcc that we are
using 'g5' as a fixed register, so some part of your build isn't using
the:

KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare

from arch/sparc/Makefile for some reason.