Commit a2a34d14 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Test all immutable non-format bits in PERF_CAPABILITIES 

Add negative testing of all immutable bits in PERF_CAPABILITIES, i.e.
single bits that are reserved-0 or are effectively reserved-1 by KVM.

Omit LBR and PEBS format bits from the test as it's easier to test them
manually than it is to add safeguards to the comment path, e.g. toggling
a single bit can yield a format of '0', which is legal as a "disable"
value.

Link: https://lore.kernel.org/r/20230311004618.920745-16-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 37f4e79c

tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c

+27 −3
Original line number Diff line number Diff line
@@ -49,6 +49,11 @@ static const union perf_capabilities immutable_caps = { 
	.pebs_baseline = 1,

};



static const union perf_capabilities format_caps = {

	.lbr_format = -1,

	.pebs_format = -1,

};



static void guest_code(void)

{

	wrmsr(MSR_IA32_PERF_CAPABILITIES, PMU_CAP_LBR_FMT);
@@ -91,12 +96,30 @@ static void test_fungible_perf_capabilities(union perf_capabilities host_cap) 
	kvm_vm_free(vm);

}



/*

 * Verify KVM rejects attempts to set unsupported and/or immutable features in

 * PERF_CAPABILITIES.  Note, LBR format and PEBS format need to be validated

 * separately as they are multi-bit values, e.g. toggling or setting a single

 * bit can generate a false positive without dedicated safeguards.

 */

static void test_immutable_perf_capabilities(union perf_capabilities host_cap)

{

	const uint64_t reserved_caps = (~host_cap.capabilities |

					immutable_caps.capabilities) &

				       ~format_caps.capabilities;



	struct kvm_vcpu *vcpu;

	struct kvm_vm *vm = vm_create_with_one_vcpu(&vcpu, NULL);

	uint64_t val;

	int ret;

	int r, bit;



	for_each_set_bit(bit, &reserved_caps, 64) {

		r = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES,

				  host_cap.capabilities ^ BIT_ULL(bit));

		TEST_ASSERT(!r, "%s immutable feature 0x%llx (bit %d) didn't fail",

			    host_cap.capabilities & BIT_ULL(bit) ? "Setting" : "Clearing",

			    BIT_ULL(bit), bit);

	}



	/*

	 * KVM only supports the host's native LBR format, as well as '0' (to
@@ -106,9 +129,10 @@ static void test_immutable_perf_capabilities(union perf_capabilities host_cap) 
		if (val == (host_cap.capabilities & PMU_CAP_LBR_FMT))

			continue;



		ret = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);

		TEST_ASSERT(!ret, "Bad LBR FMT = 0x%lx didn't fail", val);

		r = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);

		TEST_ASSERT(!r, "Bad LBR FMT = 0x%lx didn't fail", val);

	}



	kvm_vm_free(vm);

}