Sean Christopherson <seanjc@xxxxxxxxxx> writes:
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.
Sure but since I might need it and don't see why the performance cost
matters for a test that is only calling it a few times, I thought the
code looked nicer to just read it up front when I declare the variable.
I can change it.
+
+ 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);
}
Point taken. I'll go with the macro.
+
Unnecessary newline.
Will delete
+}
+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'll avoid that in the future
I would also prefer to have consistent naming between the Intel and AMD
tests
(the Intel test uses base_<name>_msr).
Done
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.
Done
+ 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;
Yes they are logically equivalent. I thought it was clearer by
emphasizing it was the negation of "i is a valid counter" (i <
nr_counters)
But I'll change it
+ uint8_t vector;
+ uint64_t val;
+
+ /* Test event selection register. */
This is pretty obvious if the MSR is named eventsel_msr.
Will delete
+ 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.
Will delete
+ 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
