From 4caadd04f62104997cbf3c71364b0509e7b64108 Mon Sep 17 00:00:00 2001
From: Suchit Karunakaran <suchitkarunakaran@gmail.com>
Date: Sun, 31 May 2026 01:25:10 +0530
Subject: [PATCH] perf build: Compile BPF skeletons with -mcpu=v3

The lock_contention BPF program uses __sync_val_compare_and_swap() to
atomically update the max_time and min_time fields in contention_data.

This builtin lowers to the BPF_CMPXCHG instruction, which is only
available in BPF ISA v3. Without an explicit -mcpu flag, Clang targets
BPF v1/v2 by default on older toolchains (Clang < 18), causing build
errors when v3 instructions are emitted.

Add -mcpu=v3 to CLANG_OPTIONS, which is used exclusively in the BPF
skeleton compilation rule.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suchit Karunakaran <suchitkarunakaran@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/bpf_skel.mak | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/bpf_skel.mak b/tools/perf/bpf_skel.mak
index 7704e7e635d8..f2559de39f96 100644
--- a/tools/perf/bpf_skel.mak
+++ b/tools/perf/bpf_skel.mak
@@ -29,7 +29,7 @@ ifneq ($(CROSS_COMPILE),)
 CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
 endif
 
-CLANG_OPTIONS = -Wall
+CLANG_OPTIONS = -Wall -mcpu=v3
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
 LIBBPF_INCLUDE := $(abspath $(or $(OUTPUT),.))/libbpf/include
 BPF_INCLUDE := -I$(SKEL_TMP_OUT)/.. -I$(SKEL_TOOL_OUT) -I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES)