[v7,12/19] KVM: selftests: Test consistency of CPUID with num of fixed counters

  From: Jinrong Liang <cloudliang@tencent.com>

Extend the PMU counters test to verify KVM emulation of fixed counters in
addition to general purpose counters.  Fixed counters add an extra wrinkle
in the form of an extra supported bitmask.  Thus quoth the SDM:

  fixed-function performance counter 'i' is supported if ECX[i] || (EDX[4:0] > i)

Test that KVM handles a counter being available through either method.

Co-developed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 .../selftests/kvm/x86_64/pmu_counters_test.c  | 60 ++++++++++++++++++-
 1 file changed, 57 insertions(+), 3 deletions(-)
  

On 11/8/2023 8:31 AM, Sean Christopherson wrote:
> From: Jinrong Liang <cloudliang@tencent.com>
>
> Extend the PMU counters test to verify KVM emulation of fixed counters in
> addition to general purpose counters.  Fixed counters add an extra wrinkle
> in the form of an extra supported bitmask.  Thus quoth the SDM:
>
>    fixed-function performance counter 'i' is supported if ECX[i] || (EDX[4:0] > i)
>
> Test that KVM handles a counter being available through either method.
>
> Co-developed-by: Like Xu <likexu@tencent.com>
> Signed-off-by: Like Xu <likexu@tencent.com>
> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   .../selftests/kvm/x86_64/pmu_counters_test.c  | 60 ++++++++++++++++++-
>   1 file changed, 57 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> index 6f2d3a64a118..8c934e261f2d 100644
> --- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> @@ -285,13 +285,19 @@ __GUEST_ASSERT(expect_gp ? vector == GP_VECTOR : !vector,			\
>   	       expect_gp ? "#GP" : "no fault", msr, vector)			\
>   
>   static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters,
> -				 uint8_t nr_counters)
> +				 uint8_t nr_counters, uint32_t or_mask)


'or_mask' doesn't show a clear meaning, "counters_bitmap" may be a 
better name.

Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>


>   {
>   	uint8_t i;
>   
>   	for (i = 0; i < nr_possible_counters; i++) {
>   		const uint32_t msr = base_msr + i;
> -		const bool expect_success = i < nr_counters;
> +
> +		/*
> +		 * Fixed counters are supported if the counter is less than the
> +		 * number of enumerated contiguous counters *or* the counter is
> +		 * explicitly enumerated in the supported counters mask.
> +		 */
> +		const bool expect_success = i < nr_counters || (or_mask & BIT(i));
>   
>   		/*
>   		 * KVM drops writes to MSR_P6_PERFCTR[0|1] if the counters are
> @@ -335,7 +341,7 @@ static void guest_test_gp_counters(void)
>   	else
>   		base_msr = MSR_IA32_PERFCTR0;
>   
> -	guest_rd_wr_counters(base_msr, MAX_NR_GP_COUNTERS, nr_gp_counters);
> +	guest_rd_wr_counters(base_msr, MAX_NR_GP_COUNTERS, nr_gp_counters, 0);
>   }
>   
>   static void test_gp_counters(uint8_t pmu_version, uint64_t perf_capabilities,
> @@ -355,9 +361,50 @@ static void test_gp_counters(uint8_t pmu_version, uint64_t perf_capabilities,
>   	kvm_vm_free(vm);
>   }
>   
> +static void guest_test_fixed_counters(void)
> +{
> +	uint64_t supported_bitmask = 0;
> +	uint8_t nr_fixed_counters = 0;
> +
> +	/* Fixed counters require Architectural vPMU Version 2+. */
> +	if (guest_get_pmu_version() >= 2)
> +		nr_fixed_counters = this_cpu_property(X86_PROPERTY_PMU_NR_FIXED_COUNTERS);
> +
> +	/*
> +	 * The supported bitmask for fixed counters was introduced in PMU
> +	 * version 5.
> +	 */
> +	if (guest_get_pmu_version() >= 5)
> +		supported_bitmask = this_cpu_property(X86_PROPERTY_PMU_FIXED_COUNTERS_BITMASK);
> +
> +	guest_rd_wr_counters(MSR_CORE_PERF_FIXED_CTR0, MAX_NR_FIXED_COUNTERS,
> +			     nr_fixed_counters, supported_bitmask);
> +}
> +
> +static void test_fixed_counters(uint8_t pmu_version, uint64_t perf_capabilities,
> +				uint8_t nr_fixed_counters,
> +				uint32_t supported_bitmask)
> +{
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_vm *vm;
> +
> +	vm = pmu_vm_create_with_one_vcpu(&vcpu, guest_test_fixed_counters,
> +					 pmu_version, perf_capabilities);
> +
> +	vcpu_set_cpuid_property(vcpu, X86_PROPERTY_PMU_FIXED_COUNTERS_BITMASK,
> +				supported_bitmask);
> +	vcpu_set_cpuid_property(vcpu, X86_PROPERTY_PMU_NR_FIXED_COUNTERS,
> +				nr_fixed_counters);
> +
> +	run_vcpu(vcpu);
> +
> +	kvm_vm_free(vm);
> +}
> +
>   static void test_intel_counters(void)
>   {
>   	uint8_t nr_arch_events = kvm_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
> +	uint8_t nr_fixed_counters = kvm_cpu_property(X86_PROPERTY_PMU_NR_FIXED_COUNTERS);
>   	uint8_t nr_gp_counters = kvm_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);
>   	uint8_t pmu_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION);
>   	unsigned int i;
> @@ -427,6 +474,13 @@ static void test_intel_counters(void)
>   				v, perf_caps[i]);
>   			for (j = 0; j <= nr_gp_counters; j++)
>   				test_gp_counters(v, perf_caps[i], j);
> +
> +			pr_info("Testing fixed counters, PMU version %u, perf_caps = %lx\n",
> +				v, perf_caps[i]);
> +			for (j = 0; j <= nr_fixed_counters; j++) {
> +				for (k = 0; k <= (BIT(nr_fixed_counters) - 1); k++)
> +					test_fixed_counters(v, perf_caps[i], j, k);
> +			}
>   		}
>   	}
>   }
  

On Thu, Nov 09, 2023, Dapeng Mi wrote:
> 
> On 11/8/2023 8:31 AM, Sean Christopherson wrote:
> > From: Jinrong Liang <cloudliang@tencent.com>
> > 
> > Extend the PMU counters test to verify KVM emulation of fixed counters in
> > addition to general purpose counters.  Fixed counters add an extra wrinkle
> > in the form of an extra supported bitmask.  Thus quoth the SDM:
> > 
> >    fixed-function performance counter 'i' is supported if ECX[i] || (EDX[4:0] > i)
> > 
> > Test that KVM handles a counter being available through either method.
> > 
> > Co-developed-by: Like Xu <likexu@tencent.com>
> > Signed-off-by: Like Xu <likexu@tencent.com>
> > Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> > Co-developed-by: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> >   .../selftests/kvm/x86_64/pmu_counters_test.c  | 60 ++++++++++++++++++-
> >   1 file changed, 57 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> > index 6f2d3a64a118..8c934e261f2d 100644
> > --- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> > +++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> > @@ -285,13 +285,19 @@ __GUEST_ASSERT(expect_gp ? vector == GP_VECTOR : !vector,			\
> >   	       expect_gp ? "#GP" : "no fault", msr, vector)			\
> >   static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters,
> > -				 uint8_t nr_counters)
> > +				 uint8_t nr_counters, uint32_t or_mask)
> 
> 
> 'or_mask' doesn't show a clear meaning, "counters_bitmap" may be a better
> name.

I don't love "or_mask" either, but I like "counters_bitmap" far less, as it doesn't
provide any hint as to the polarity or behavior.  Readers that aren't familiar with
the kludgy enumeration of PMCs in CPUID won't already know that it's a mask that's
OR-d in, e.g. counters_bitmap could be a replacement, it could be an AND-mask, it
could be something entirely unrelated.  I opted for a name that describe the behavior
because I don't see a way to succintly capture the (IMO) weird enumeration.