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perf/x86/intel/p4: Fix unused variable warning in p4_pmu_init()

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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 <dave.hansen@linux.intel.com>
Signed-off-by: Aldo Conte <aldocontelk@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260320112302.281549-1-aldocontelk@gmail.com
This commit is contained in:
Aldo Conte 2026-03-20 12:23:02 +01:00 committed by Peter Zijlstra
parent b191aa32be
commit 6ee26b7a22
1 changed files with 3 additions and 3 deletions
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6
arch/x86/events/intel/p4.c
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@ -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;