KVM: arm64: selftests: Use the vCPU attr for setting nr of PMU counters

Configuring the number of implemented counters via PMCR_EL0.N was a bad
idea in retrospect as it interacts poorly with nested. Migrate the
selftest to use the vCPU attribute instead of the KVM_SET_ONE_REG
mechanism.

Signed-off-by: Oliver Upton <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

tools/testing/selftests/kvm/arm64/vpmu_counter_access.c

···
 	return FIELD_GET(ARMV8_PMU_PMCR_N, pmcr);
 }
 
-static void set_pmcr_n(uint64_t *pmcr, uint64_t pmcr_n)
-{
-	u64p_replace_bits((__u64 *) pmcr, pmcr_n, ARMV8_PMU_PMCR_N);
-}
-
 static uint64_t get_counters_mask(uint64_t n)
 {
 	uint64_t mask = BIT(ARMV8_PMU_CYCLE_IDX);
···
 		.attr = KVM_ARM_VCPU_PMU_V3_IRQ,
 		.addr = (uint64_t)&irq,
 	};
-	struct kvm_device_attr init_attr = {
-		.group = KVM_ARM_VCPU_PMU_V3_CTRL,
-		.attr = KVM_ARM_VCPU_PMU_V3_INIT,
-	};
 
 	/* The test creates the vpmu_vm multiple times. Ensure a clean state */
 	memset(&vpmu_vm, 0, sizeof(vpmu_vm));
···
 		    pmuver >= ID_AA64DFR0_EL1_PMUVer_IMP,
 		    "Unexpected PMUVER (0x%x) on the vCPU with PMUv3", pmuver);
 
-	/* Initialize vPMU */
 	vcpu_ioctl(vpmu_vm.vcpu, KVM_SET_DEVICE_ATTR, &irq_attr);
-	vcpu_ioctl(vpmu_vm.vcpu, KVM_SET_DEVICE_ATTR, &init_attr);
 }
 
 static void destroy_vpmu_vm(void)
···
 	}
 }
 
-static void test_create_vpmu_vm_with_pmcr_n(uint64_t pmcr_n, bool expect_fail)
+static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters, bool expect_fail)
 {
 	struct kvm_vcpu *vcpu;
-	uint64_t pmcr, pmcr_orig;
+	unsigned int prev;
+	int ret;
 
 	create_vpmu_vm(guest_code);
 	vcpu = vpmu_vm.vcpu;
 
-	pmcr_orig = vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0));
-	pmcr = pmcr_orig;
+	prev = get_pmcr_n(vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0)));
 
-	/*
-	 * Setting a larger value of PMCR.N should not modify the field, and
-	 * return a success.
-	 */
-	set_pmcr_n(&pmcr, pmcr_n);
-	vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), pmcr);
-	pmcr = vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0));
+	ret = __vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+				     KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS, &nr_counters);
 
 	if (expect_fail)
-		TEST_ASSERT(pmcr_orig == pmcr,
-			    "PMCR.N modified by KVM to a larger value (PMCR: 0x%lx) for pmcr_n: 0x%lx",
-			    pmcr, pmcr_n);
+		TEST_ASSERT(ret && errno == EINVAL,
+			    "Setting more PMU counters (%u) than available (%u) unexpectedly succeeded",
+			    nr_counters, prev);
 	else
-		TEST_ASSERT(pmcr_n == get_pmcr_n(pmcr),
-			    "Failed to update PMCR.N to %lu (received: %lu)",
-			    pmcr_n, get_pmcr_n(pmcr));
+		TEST_ASSERT(!ret, KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
+
+	vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL, KVM_ARM_VCPU_PMU_V3_INIT, NULL);
 }
 
 /*
···
 
 	pr_debug("Test with pmcr_n %lu\n", pmcr_n);
 
-	test_create_vpmu_vm_with_pmcr_n(pmcr_n, false);
+	test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
 	vcpu = vpmu_vm.vcpu;
 
 	/* Save the initial sp to restore them later to run the guest again */
···
 	uint64_t set_reg_id, clr_reg_id, reg_val;
 	uint64_t valid_counters_mask, max_counters_mask;
 
-	test_create_vpmu_vm_with_pmcr_n(pmcr_n, false);
+	test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
 	vcpu = vpmu_vm.vcpu;
 
 	valid_counters_mask = get_counters_mask(pmcr_n);
···
 {
 	pr_debug("Error test with pmcr_n %lu (larger than the host)\n", pmcr_n);
 
-	test_create_vpmu_vm_with_pmcr_n(pmcr_n, true);
+	test_create_vpmu_vm_with_nr_counters(pmcr_n, true);
 	destroy_vpmu_vm();
 }
 
···
 	return get_pmcr_n(pmcr);
 }
 
+static bool kvm_supports_nr_counters_attr(void)
+{
+	bool supported;
+
+	create_vpmu_vm(NULL);
+	supported = !__vcpu_has_device_attr(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+					    KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS);
+	destroy_vpmu_vm();
+
+	return supported;
+}
+
 int main(void)
 {
 	uint64_t i, pmcr_n;
 
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_ARM_PMU_V3));
 	TEST_REQUIRE(kvm_supports_vgic_v3());
+	TEST_REQUIRE(kvm_supports_nr_counters_attr());
 
 	pmcr_n = get_pmcr_n_limit();
 	for (i = 0; i <= pmcr_n; i++) {