linux-kernel - Re: [PATCH v3 2/5] KVM: selftests: Track unavailable

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Message-ID: <8e3faa80-7091-454b-8ac6-1aa431185c06@linux.intel.com>
Date: Fri, 19 Sep 2025 13:43:49 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Yi Lai <yi1.lai@...el.com>, dongsheng <dongsheng.x.zhang@...el.com>
Subject: Re: [PATCH v3 2/5] KVM: selftests: Track unavailable_mask for PMU
 events as 32-bit value


On 9/19/2025 8:45 AM, Sean Christopherson wrote:
> Track the mask of "unavailable" PMU events as a 32-bit value.  While bits
> 31:9 are currently reserved, silently truncating those bits is unnecessary
> and asking for missed coverage.  To avoid running afoul of the sanity check
> in vcpu_set_cpuid_property(), explicitly adjust the mask based on the
> non-reserved bits as reported by KVM's supported CPUID.
>
> Opportunistically update the "all ones" testcase to pass -1u instead of
> 0xff.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  tools/testing/selftests/kvm/x86/pmu_counters_test.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86/pmu_counters_test.c b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
> index 8aaaf25b6111..cfeed0103341 100644
> --- a/tools/testing/selftests/kvm/x86/pmu_counters_test.c
> +++ b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
> @@ -311,7 +311,7 @@ static void guest_test_arch_events(void)
>  }
>  
>  static void test_arch_events(uint8_t pmu_version, uint64_t perf_capabilities,
> -			     uint8_t length, uint8_t unavailable_mask)
> +			     uint8_t length, uint32_t unavailable_mask)
>  {
>  	struct kvm_vcpu *vcpu;
>  	struct kvm_vm *vm;
> @@ -320,6 +320,9 @@ static void test_arch_events(uint8_t pmu_version, uint64_t perf_capabilities,
>  	if (!pmu_version)
>  		return;
>  
> +	unavailable_mask = GENMASK(X86_PROPERTY_PMU_EVENTS_MASK.hi_bit,
> +				   X86_PROPERTY_PMU_EVENTS_MASK.lo_bit);

Should be "unavailable_mask &="? Otherwise the incoming argument
"unavailable_mask" would be overwritten unconditionally. 


> +
>  	vm = pmu_vm_create_with_one_vcpu(&vcpu, guest_test_arch_events,
>  					 pmu_version, perf_capabilities);
>  
> @@ -630,7 +633,7 @@ static void test_intel_counters(void)
>  			 */
>  			for (j = 0; j <= NR_INTEL_ARCH_EVENTS + 1; j++) {
>  				test_arch_events(v, perf_caps[i], j, 0);
> -				test_arch_events(v, perf_caps[i], j, 0xff);
> +				test_arch_events(v, perf_caps[i], j, -1u);
>  
>  				for (k = 0; k < NR_INTEL_ARCH_EVENTS; k++)
>  					test_arch_events(v, perf_caps[i], j, BIT(k));