Commit 1fcd3053 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Reduce number of "unavailable PMU events" combos tested 



Reduce the number of combinations of unavailable PMU events masks that are
testing by the PMU counters test.  In reality, testing every possible
combination isn't all that interesting, and certainly not worth the tens
of seconds (or worse, minutes) of runtime.  Fully testing the N^2 space
will be especially problematic in the near future, as 5! new arch events
are on their way.

Use alternating bit patterns (and 0 and -1u) in the hopes that _if_ there
is ever a KVM bug, it's not something horribly convoluted that shows up
only with a super specific pattern/value.

Reported-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Reviewed-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20250919214648.1585683-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 571fc283

tools/testing/selftests/kvm/x86/pmu_counters_test.c

+23 −15
Original line number Diff line number Diff line
@@ -577,6 +577,26 @@ static void test_intel_counters(void) 
		PMU_CAP_FW_WRITES,

	};



	/*

	 * To keep the total runtime reasonable, test only a handful of select,

	 * semi-arbitrary values for the mask of unavailable PMU events.  Test

	 * 0 (all events available) and all ones (no events available) as well

	 * as alternating bit sequencues, e.g. to detect if KVM is checking the

	 * wrong bit(s).

	 */

	const uint32_t unavailable_masks[] = {

		0x0,

		0xffffffffu,

		0xaaaaaaaau,

		0x55555555u,

		0xf0f0f0f0u,

		0x0f0f0f0fu,

		0xa0a0a0a0u,

		0x0a0a0a0au,

		0x50505050u,

		0x05050505u,

	};



	/*

	 * Test up to PMU v5, which is the current maximum version defined by

	 * Intel, i.e. is the last version that is guaranteed to be backwards
@@ -614,16 +634,7 @@ static void test_intel_counters(void) 


			pr_info("Testing arch events, PMU version %u, perf_caps = %lx\n",

				v, perf_caps[i]);

			/*

			 * To keep the total runtime reasonable, test every

			 * possible non-zero, non-reserved bitmap combination

			 * only with the native PMU version and the full bit

			 * vector length.

			 */

			if (v == pmu_version) {

				for (k = 1; k < (BIT(NR_INTEL_ARCH_EVENTS) - 1); k++)

					test_arch_events(v, perf_caps[i], NR_INTEL_ARCH_EVENTS, k);

			}



			/*

			 * Test single bits for all PMU version and lengths up

			 * the number of events +1 (to verify KVM doesn't do
@@ -632,11 +643,8 @@ static void test_intel_counters(void) 
			 * ones i.e. all events being available and unavailable.

			 */

			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, -1u);



				for (k = 0; k < NR_INTEL_ARCH_EVENTS; k++)

					test_arch_events(v, perf_caps[i], j, BIT(k));

				for (k = 1; k < ARRAY_SIZE(unavailable_masks); k++)

					test_arch_events(v, perf_caps[i], j, unavailable_masks[k]);

			}



			pr_info("Testing GP counters, PMU version %u, perf_caps = %lx\n",