On 1/31/2024 7:27 AM, Sean Christopherson wrote:
On Mon, Jan 15, 2024, Dapeng Mi wrote:
On 1/13/2024 5:37 AM, Sean Christopherson wrote:
On Fri, Jan 12, 2024, Dapeng Mi wrote:
On 1/10/2024 7:02 AM, Sean Christopherson wrote:
+/*
+ * If an architectural event is supported and guaranteed to generate at least
+ * one "hit, assert that its count is non-zero. If an event isn't supported or
+ * the test can't guarantee the associated action will occur, then all bets are
+ * off regarding the count, i.e. no checks can be done.
+ *
+ * Sanity check that in all cases, the event doesn't count when it's disabled,
+ * and that KVM correctly emulates the write of an arbitrary value.
+ */
+static void guest_assert_event_count(uint8_t idx,
+ struct kvm_x86_pmu_feature event,
+ uint32_t pmc, uint32_t pmc_msr)
+{
+ uint64_t count;
+
+ count = _rdpmc(pmc);
+ if (!this_pmu_has(event))
+ goto sanity_checks;
+
+ switch (idx) {
+ case INTEL_ARCH_INSTRUCTIONS_RETIRED_INDEX:
+ GUEST_ASSERT_EQ(count, NUM_INSNS_RETIRED);
+ break;
+ case INTEL_ARCH_BRANCHES_RETIRED_INDEX:
+ GUEST_ASSERT_EQ(count, NUM_BRANCHES);
+ break;
+ case INTEL_ARCH_CPU_CYCLES_INDEX:
+ case INTEL_ARCH_REFERENCE_CYCLES_INDEX:
Since we already support slots event in below guest_test_arch_event(), we
can add check for INTEL_ARCH_TOPDOWN_SLOTS_INDEX here.
Can that actually be tested at this point, since KVM doesn't support
X86_PMU_FEATURE_TOPDOWN_SLOTS, i.e. this_pmu_has() above should always fail, no?
I suppose X86_PMU_FEATURE_TOPDOWN_SLOTS has been supported in KVM. The
following output comes from a guest with latest kvm-x86 code on the Sapphire
Rapids platform.
sudo cpuid -l 0xa
CPU 0:
Architecture Performance Monitoring Features (0xa):
version ID = 0x2 (2)
number of counters per logical processor = 0x8 (8)
bit width of counter = 0x30 (48)
length of EBX bit vector = 0x8 (8)
core cycle event = available
instruction retired event = available
reference cycles event = available
last-level cache ref event = available
last-level cache miss event = available
branch inst retired event = available
branch mispred retired event = available
top-down slots event = available
Current KVM doesn't support fixed counter 3 and pseudo slots event yet, but
the architectural slots event is supported and can be programed on a GP
counter. Current test code can cover this case, so I think we'd better add
the check for the slots count.
Can you submit a patch on top, with a changelog that includes justification that
that explains exactly what assertions can be made on the top-down slots event
given the "workload" being measured? I'm definitely not opposed to adding coverage
for top-down slots, but at this point, I don't want to respin this series, nor do
I want to make that change when applying on the fly.
Yeah, I'm glad to submit a patch for this. :)
BTW, I have a patch series to do the bug fixes and improvements for
kvm-unit-tests/pmu test. (some improvement ideas come from this patchset.)
https://lore.kernel.org/kvm/20240103031409.2504051-1-dapeng1.mi@xxxxxxxxxxxxxxx/
Could you please kindly review them? Thanks.
