[PATCH] perf/x86/intel/pt: rdmsr before the CPUID test produces KVM warning

From: Huaitong Han
Date: Mon Aug 31 2015 - 04:21:32 EST

If KVM does not support INTEL_PT, guest MSR_IA32_RTIT_CTL reading will
produce host warning like "kvm [2469]: vcpu0 unhandled rdmsr: 0x570".

Guest can determine whether the CPU supports Intel_PT according to CPUID,
so test_cpu_cap function is added before rdmsr,and it is more in line with
the code style.

Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>
Reviewed-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 183de71..4cc6492 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -123,9 +123,6 @@ static int __init pt_pmu_hw_init(void)
long i;

attrs = NULL;
- ret = -ENODEV;
- if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT))
- goto fail;

for (i = 0; i < PT_CPUID_LEAVES; i++) {
cpuid_count(20, i,
@@ -1061,6 +1058,10 @@ static __init int pt_init(void)
int ret, cpu, prior_warn = 0;

BUILD_BUG_ON(sizeof(struct topa) > PAGE_SIZE);
+ if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT))
+ return -ENODEV;
for_each_online_cpu(cpu) {
u64 ctl;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/