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    Subject[PATCH v8 13/13] KVM: selftests: aarch64: vPMU test for immutability
    From
    KVM marks some of the vPMU registers as immutable to
    userspace once the vCPU has started running. Add a test
    scenario to check this behavior.

    Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
    ---
    .../kvm/aarch64/vpmu_counter_access.c | 47 ++++++++++++++++++-
    1 file changed, 46 insertions(+), 1 deletion(-)

    diff --git a/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
    index 2b697b144e677..f87d76c614e8b 100644
    --- a/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
    +++ b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
    @@ -9,7 +9,8 @@
    * those counters, and if the guest is prevented from accessing any
    * other counters.
    * It also checks if the userspace accesses to the PMU regsisters honor the
    - * PMCR.N value that's set for the guest.
    + * PMCR.N value that's set for the guest and if these accesses are immutable
    + * after KVM has run once.
    * This test runs only when KVM_CAP_ARM_PMU_V3 is supported on the host.
    */
    #include <kvm_util.h>
    @@ -648,6 +649,48 @@ static void run_error_test(uint64_t pmcr_n)
    destroy_vpmu_vm();
    }

    +static uint64_t immutable_regs[] = {
    + SYS_PMCR_EL0,
    + SYS_PMCNTENSET_EL0,
    + SYS_PMCNTENCLR_EL0,
    + SYS_PMINTENSET_EL1,
    + SYS_PMINTENCLR_EL1,
    + SYS_PMOVSSET_EL0,
    + SYS_PMOVSCLR_EL0,
    +};
    +
    +/*
    + * Create a guest with one vCPU, run it, and then make an attempt to update
    + * the registers in @immutable_regs[] (with their complements). KVM shouldn't
    + * allow updating these registers once vCPU starts running. Hence, the test
    + * fails if that's not the case.
    + */
    +static void run_immutable_test(uint64_t pmcr_n)
    +{
    + int i;
    + struct kvm_vcpu *vcpu;
    + uint64_t reg_id, reg_val, reg_val_orig;
    +
    + create_vpmu_vm(guest_code);
    + vcpu = vpmu_vm.vcpu;
    +
    + run_vcpu(vcpu, pmcr_n);
    +
    + for (i = 0; i < ARRAY_SIZE(immutable_regs); i++) {
    + reg_id = immutable_regs[i];
    +
    + vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(reg_id), &reg_val_orig);
    + vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(reg_id), ~reg_val_orig);
    + vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(reg_id), &reg_val);
    +
    + TEST_ASSERT(reg_val == reg_val_orig,
    + "Register 0x%llx value updated after vCPU run: 0x%lx; expected: 0x%lx\n",
    + KVM_ARM64_SYS_REG(reg_id), reg_val, reg_val_orig);
    + }
    +
    + destroy_vpmu_vm();
    +}
    +
    /*
    * Return the default number of implemented PMU event counters excluding
    * the cycle counter (i.e. PMCR_EL0.N value) for the guest.
    @@ -677,5 +720,7 @@ int main(void)
    for (i = pmcr_n + 1; i < ARMV8_PMU_MAX_COUNTERS; i++)
    run_error_test(i);

    + run_immutable_test(pmcr_n);
    +
    return 0;
    }
    --
    2.42.0.655.g421f12c284-goog
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