On Wed, Sep 18, 2024, Colton Lewis wrote:
> Run a basic test to ensure we can write an arbitrary value to the core
> counters and read it back.
>
> Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
> ---
> .../selftests/kvm/x86_64/pmu_counters_test.c | 54 +++++++++++++++++++
> 1 file changed, 54 insertions(+)
>
> 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 5b240585edc5..79ca7d608e00 100644
> --- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> @@ -641,11 +641,65 @@ static uint8_t nr_core_counters(void)
> return AMD_NR_CORE_EXT_COUNTERS;
>
> return AMD_NR_CORE_COUNTERS;
> +}
> +
> +static uint8_t guest_nr_core_counters(void)
> +{
> + uint8_t nr_counters = this_cpu_property(X86_PROPERTY_NUM_PERF_CTR_CORE);
> + bool core_ext = this_cpu_has(X86_FEATURE_PERF_CTR_EXT_CORE);
For both this and nr_core_counters(), there's no need to read PERF_CTR_EXT_CORE
if nr_counters is non-zero, and then no need to capture it in a local variable.
> +
> + if (nr_counters != 0)
> + return nr_counters;
> +
> + if (core_ext)
> + return AMD_NR_CORE_EXT_COUNTERS;
> +
> + return AMD_NR_CORE_COUNTERS;
This is *painfully* similar to nr_core_counters(). It actually took me almost
a minute of staring to see the difference. One option would be to add a helper
to dedup the if-statements, but while somewhat gross, I actually think a macro
is the way to go.
#define nr_core_counters(scope) \
({ \
uint8_t nr_counters = scope##_cpu_property(X86_PROPERTY_NR_PERFCTR_CORE); \
\
if (!nr_counters) { \
if (scope##_cpu_has(X86_FEATURE_PERFCTR_CORE)) \
nr_counters = AMD_NR_CORE_EXT_COUNTERS; \
else \
nr_counters = AMD_NR_CORE_COUNTERS; \
} \
nr_counters; \
})
static uint8_t kvm_nr_core_counters(void)
{
return nr_core_counters(kvm);
}
static uint8_t guest_nr_core_counters(void)
{
return nr_core_counters(this);
}
> +
Unnecessary newline.
> +}
>
> +static void guest_test_rdwr_core_counters(void)
> +{
> + bool core_ext = this_cpu_has(X86_FEATURE_PERF_CTR_EXT_CORE);
> + uint8_t nr_counters = guest_nr_core_counters();
> + uint8_t i;
> + uint32_t esel_msr_base = core_ext ? MSR_F15H_PERF_CTL : MSR_K7_EVNTSEL0;
Please don't concoct new abbreviations. "esel" isn't used anywhere in KVM, and
AFAICT it's not used in perf either.
I would also prefer to have consistent naming between the Intel and AMD tests
(the Intel test uses base_<name>_msr).
base_eventsel_msr is all of four characters more.
> + uint32_t cnt_msr_base = core_ext ? MSR_F15H_PERF_CTR : MSR_K7_PERFCTR0;
For better or worse, the Intel version uses "base_pmc_msr". I see no reason to
diverage from that.
> + uint32_t msr_step = core_ext ? 2 : 1;
> +
> + for (i = 0; i < AMD_NR_CORE_EXT_COUNTERS; i++) {
> + uint64_t test_val = 0xffff;
> + uint32_t esel_msr = esel_msr_base + msr_step * i;
> + uint32_t cnt_msr = cnt_msr_base + msr_step * i;
And then
uint32_t eventsel_msr = ...;
uint32_t pmc_msr = ...;
> + bool expect_gp = !(i < nr_counters);
Uh, isn't that just a weird way of writing:
bool expect_gp = i >= nr_counters;
> + uint8_t vector;
> + uint64_t val;
> +
> + /* Test event selection register. */
This is pretty obvious if the MSR is named eventsel_msr.
> + vector = wrmsr_safe(esel_msr, test_val);
> + GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, esel_msr, expect_gp, vector);
> +
> + vector = rdmsr_safe(esel_msr, &val);
> + GUEST_ASSERT_PMC_MSR_ACCESS(RDMSR, esel_msr, expect_gp, vector);
> +
> + if (!expect_gp)
> + GUEST_ASSERT_PMC_VALUE(RDMSR, esel_msr, val, test_val);
> +
> + /* Test counter register. */
Same thing here. If there is novel information/behavior, then by all means add
a comment.
> + vector = wrmsr_safe(cnt_msr, test_val);
> + GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, cnt_msr, expect_gp, vector);
> +
> + vector = rdmsr_safe(cnt_msr, &val);
> + GUEST_ASSERT_PMC_MSR_ACCESS(RDMSR, cnt_msr, expect_gp, vector);
> +
> + if (!expect_gp)
> + GUEST_ASSERT_PMC_VALUE(RDMSR, cnt_msr, val, test_val);
> + }
> }
>
> static void guest_test_core_counters(void)
> {
> + guest_test_rdwr_core_counters();
> GUEST_DONE();
> }
>
> --
> 2.46.0.662.g92d0881bb0-goog
>
