Re: [PATCH v2 7/7] KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never lost

Maxim Levitsky
2021-05-24T12:36:53Z

On Mon, 2021-05-17 at 15:50 +0200, Vitaly Kuznetsov wrote:
> Do KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE for a freshly restored VM
> (before the first KVM_RUN) to check that KVM_STATE_NESTED_EVMCS is not
> lost.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> .../testing/selftests/kvm/x86_64/evmcs_test.c | 64 +++++++++++--------
> 1 file changed, 38 insertions(+), 26 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/evmcs_test.c b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
> index 63096cea26c6..fcef347a681a 100644
> --- a/tools/testing/selftests/kvm/x86_64/evmcs_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
> @@ -121,14 +121,38 @@ void inject_nmi(struct kvm_vm *vm)
> vcpu_events_set(vm, VCPU_ID, &events);
> }
>
> +static void save_restore_vm(struct kvm_vm *vm)
> +{
> + struct kvm_regs regs1, regs2;
> + struct kvm_x86_state *state;
> +
> + state = vcpu_save_state(vm, VCPU_ID);
> + memset(&regs1, 0, sizeof(regs1));
> + vcpu_regs_get(vm, VCPU_ID, &regs1);
> +
> + kvm_vm_release(vm);
> +
> + /* Restore state in a new VM. */
> + kvm_vm_restart(vm, O_RDWR);
> + vm_vcpu_add(vm, VCPU_ID);
> + vcpu_set_hv_cpuid(vm, VCPU_ID);
> + vcpu_enable_evmcs(vm, VCPU_ID);
> + vcpu_load_state(vm, VCPU_ID, state);
> + free(state);
> +
> + memset(&regs2, 0, sizeof(regs2));
> + vcpu_regs_get(vm, VCPU_ID, &regs2);
> + TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
> + "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
> + (ulong) regs2.rdi, (ulong) regs2.rsi);
> +}
> +
> int main(int argc, char *argv[])
> {
> vm_vaddr_t vmx_pages_gva = 0;
>
> - struct kvm_regs regs1, regs2;
> struct kvm_vm *vm;
> struct kvm_run *run;
> - struct kvm_x86_state *state;
> struct ucall uc;
> int stage;
>
> @@ -145,10 +169,6 @@ int main(int argc, char *argv[])
> vcpu_set_hv_cpuid(vm, VCPU_ID);
> vcpu_enable_evmcs(vm, VCPU_ID);
>
> - run = vcpu_state(vm, VCPU_ID);
> -
> - vcpu_regs_get(vm, VCPU_ID, &regs1);
> -
> vcpu_alloc_vmx(vm, &vmx_pages_gva);
> vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_gva);
>
> @@ -160,6 +180,7 @@ int main(int argc, char *argv[])
> pr_info("Running L1 which uses EVMCS to run L2\n");
>
> for (stage = 1;; stage++) {
> + run = vcpu_state(vm, VCPU_ID);
> _vcpu_run(vm, VCPU_ID);
> TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
> "Stage %d: unexpected exit reason: %u (%s),\n",
> @@ -184,32 +205,23 @@ int main(int argc, char *argv[])
> uc.args[1] == stage, "Stage %d: Unexpected register values vmexit, got %lx",
> stage, (ulong)uc.args[1]);
>
> - state = vcpu_save_state(vm, VCPU_ID);
> - memset(&regs1, 0, sizeof(regs1));
> - vcpu_regs_get(vm, VCPU_ID, &regs1);
> -
> - kvm_vm_release(vm);
> -
> - /* Restore state in a new VM. */
> - kvm_vm_restart(vm, O_RDWR);
> - vm_vcpu_add(vm, VCPU_ID);
> - vcpu_set_hv_cpuid(vm, VCPU_ID);
> - vcpu_enable_evmcs(vm, VCPU_ID);
> - vcpu_load_state(vm, VCPU_ID, state);
> - run = vcpu_state(vm, VCPU_ID);
> - free(state);
> -
> - memset(&regs2, 0, sizeof(regs2));
> - vcpu_regs_get(vm, VCPU_ID, &regs2);
> - TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
> - "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
> - (ulong) regs2.rdi, (ulong) regs2.rsi);
> + save_restore_vm(vm);
>
> /* Force immediate L2->L1 exit before resuming */
> if (stage == 8) {
> pr_info("Injecting NMI into L1 before L2 had a chance to run after restore\n");
> inject_nmi(vm);
> }
> +
> + /*
> + * Do KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE for a freshly
> + * restored VM (before the first KVM_RUN) to check that
> + * KVM_STATE_NESTED_EVMCS is not lost.
> + */
> + if (stage == 9) {
> + pr_info("Trying extra KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE cycle\n");
> + save_restore_vm(vm);
> + }
> }
>
> done:

This is a very good test. I do think that in the future we should move save_restore_vm
to common code so that I could test SVM nested migration (and plain VMX nested migration)
in a similar way.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky