Re: [PATCH v7 10/12] KVM: selftests: aarch64: Introduce vpmu_counter_access test

[Sebastian Ott]

On Mon, 9 Oct 2023, Raghavendra Rao Ananta wrote:
> +static void guest_code(uint64_t expected_pmcr_n)
> +{
> +	uint64_t pmcr, pmcr_n;
> +
> +	__GUEST_ASSERT(expected_pmcr_n <= ARMV8_PMU_MAX_GENERAL_COUNTERS,
> +			"Expected PMCR.N: 0x%lx; ARMv8 general counters: 0x%lx",
> +			expected_pmcr_n, ARMV8_PMU_MAX_GENERAL_COUNTERS);
> +
> +	pmcr = read_sysreg(pmcr_el0);
> +	pmcr_n = get_pmcr_n(pmcr);
> +
> +	/* Make sure that PMCR_EL0.N indicates the value userspace set */
> +	__GUEST_ASSERT(pmcr_n == expected_pmcr_n,
> +			"Expected PMCR.N: 0x%lx, PMCR.N: 0x%lx",
> +			pmcr_n, expected_pmcr_n);

Expected vs read value is swapped.


Also, since the kernel has special handling for this, should we add a
test like below?

+static void immutable_test(void)
+{
+	struct kvm_vcpu *vcpu;
+	uint64_t sp, pmcr, pmcr_n;
+	struct kvm_vcpu_init init;
+
+	create_vpmu_vm(guest_code);
+
+	vcpu = vpmu_vm.vcpu;
+
+	/* Save the initial sp to restore them later to run the guest again */
+	vcpu_get_reg(vcpu, ARM64_CORE_REG(sp_el1), &sp);
+
+	vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), &pmcr);
+	pmcr_n = get_pmcr_n(pmcr);
+
+	run_vcpu(vcpu, pmcr_n);
+
+	vm_ioctl(vpmu_vm.vm, KVM_ARM_PREFERRED_TARGET, &init);
+	init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3);
+	aarch64_vcpu_setup(vcpu, &init);
+	vcpu_init_descriptor_tables(vcpu);
+	vcpu_set_reg(vcpu, ARM64_CORE_REG(sp_el1), sp);
+	vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc), (uint64_t)guest_code);
+
+	/* Update the PMCR_EL0.N after the VM ran once */
+	set_pmcr_n(&pmcr, 0);
+	vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), pmcr);
+
+	/* Verify that the guest still gets the unmodified value */
+	run_vcpu(vcpu, pmcr_n);
+
+	destroy_vpmu_vm();
+}