From 6ee26b7a224b27aa7e8e1ee8a845a31664d2e97c Mon Sep 17 00:00:00 2001 From: Aldo Conte Date: Fri, 20 Mar 2026 12:23:02 +0100 Subject: [PATCH] perf/x86/intel/p4: Fix unused variable warning in p4_pmu_init() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Build the kernel with make W=1 generates the following warning: arch/x86/events/intel/p4.c: In function ‘p4_pmu_init’: arch/x86/events/intel/p4.c:1370:27: error: variable ‘high’ set but not used [-Werror=unused-but-set-variable] 1370 | unsigned int low, high; | ^~~~ This happens because, although both variables are declared and initialized by rdmsr, only `low` is used in the subsequent if statement. This patch uses the rdmsrq() macro instead of the rdmsr() macro. The rdmsrq() macro avoids the use of high and low variables because it reads the msr value in a single u64 variable. Also, replace (1 << 7) with the proper macro. Running `make W=1` again resolves the error. I was unable to test the patch because i do not have the hardware. Suggested-by: Dave Hansen Signed-off-by: Aldo Conte Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260320112302.281549-1-aldocontelk@gmail.com --- arch/x86/events/intel/p4.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/p4.c b/arch/x86/events/intel/p4.c index e5fd7367e45d..02bfdb77158b 100644 --- a/arch/x86/events/intel/p4.c +++ b/arch/x86/events/intel/p4.c @@ -1367,14 +1367,14 @@ static __initconst const struct x86_pmu p4_pmu = { __init int p4_pmu_init(void) { - unsigned int low, high; + unsigned int misc; int i, reg; /* If we get stripped -- indexing fails */ BUILD_BUG_ON(ARCH_P4_MAX_CCCR > INTEL_PMC_MAX_GENERIC); - rdmsr(MSR_IA32_MISC_ENABLE, low, high); - if (!(low & (1 << 7))) { + rdmsrq(MSR_IA32_MISC_ENABLE, misc); + if (!(misc & MSR_IA32_MISC_ENABLE_EMON)) { pr_cont("unsupported Netburst CPU model %d ", boot_cpu_data.x86_model); return -ENODEV;