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

[Raghavendra Rao Ananta]

On Tue, Oct 17, 2023 at 8:48 AM Sebastian Ott <sebott@xxxxxxxxxx> wrote:
>
> 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.
>
Good catch! I'll fix this in v8.
>
> 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();
> +}
Thanks for the suggestion! I'll add this test case in v8.

- Raghavendra
>