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References: <20211123005036.2954379-1-pbonzini@redhat.com> <20211123005036.2954379-9-pbonzini@redhat.com>
In-Reply-To: <20211123005036.2954379-9-pbonzini@redhat.com>
From:   Peter Gonda <pgonda@google.com>
Date:   Wed, 1 Dec 2021 11:09:57 -0700
Message-ID: <CAMkAt6ouPVpRAAEhT1SgYEr3egiVCziKxV0viRiQxg7MD0dHHQ@mail.gmail.com>
Subject: Re: [PATCH 08/12] selftests: sev_migrate_tests: add tests for KVM_CAP_VM_COPY_ENC_CONTEXT_FROM
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Sean Christopherson <seanjc@google.com>
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On Mon, Nov 22, 2021 at 5:50 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> I am putting the tests in sev_migrate_tests because the failure conditions are
> very similar and some of the setup code can be reused, too.
>
> The tests cover both successful creation of a mirror VM, and error
> conditions.
>
> Cc: Peter Gonda <pgonda@google.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  .../selftests/kvm/x86_64/sev_migrate_tests.c  | 112 ++++++++++++++++--
>  1 file changed, 105 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c b/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> index 0cd7e2eaa895..d265cea5de85 100644
> --- a/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> +++ b/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> @@ -54,12 +54,15 @@ static struct kvm_vm *sev_vm_create(bool es)
>         return vm;
>  }
>
> -static struct kvm_vm *__vm_create(void)
> +static struct kvm_vm *aux_vm_create(bool with_vcpus)
>  {
>         struct kvm_vm *vm;
>         int i;
>
>         vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
> +       if (!with_vcpus)
> +               return vm;
> +
>         for (i = 0; i < NR_MIGRATE_TEST_VCPUS; ++i)
>                 vm_vcpu_add(vm, i);
>
> @@ -93,7 +96,7 @@ static void test_sev_migrate_from(bool es)
>
>         src_vm = sev_vm_create(es);
>         for (i = 0; i < NR_MIGRATE_TEST_VMS; ++i)
> -               dst_vms[i] = __vm_create();
> +               dst_vms[i] = aux_vm_create(true);
>
>         /* Initial migration from the src to the first dst. */
>         sev_migrate_from(dst_vms[0]->fd, src_vm->fd);
> @@ -162,7 +165,7 @@ static void test_sev_migrate_parameters(void)
>         sev_vm = sev_vm_create(/* es= */ false);
>         sev_es_vm = sev_vm_create(/* es= */ true);
>         vm_no_vcpu = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
> -       vm_no_sev = __vm_create();
> +       vm_no_sev = aux_vm_create(true);
>         sev_es_vm_no_vmsa = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
>         sev_ioctl(sev_es_vm_no_vmsa->fd, KVM_SEV_ES_INIT, NULL);
>         vm_vcpu_add(sev_es_vm_no_vmsa, 1);
> @@ -203,11 +206,106 @@ static void test_sev_migrate_parameters(void)
>         kvm_vm_free(vm_no_sev);
>  }
>
> +static int __sev_mirror_create(int dst_fd, int src_fd)
> +{
> +       struct kvm_enable_cap cap = {
> +               .cap = KVM_CAP_VM_COPY_ENC_CONTEXT_FROM,
> +               .args = { src_fd }
> +       };
> +
> +       return ioctl(dst_fd, KVM_ENABLE_CAP, &cap);
> +}
> +
> +
> +static void sev_mirror_create(int dst_fd, int src_fd)
> +{
> +       int ret;
> +
> +       ret = __sev_mirror_create(dst_fd, src_fd);
> +       TEST_ASSERT(!ret, "Copying context failed, ret: %d, errno: %d\n", ret, errno);
> +}
> +
> +static void test_sev_mirror(bool es)
> +{
> +       struct kvm_vm *src_vm, *dst_vm;
> +       struct kvm_sev_launch_start start = {
> +               .policy = es ? SEV_POLICY_ES : 0
> +       };
> +       int i;
> +
> +       src_vm = sev_vm_create(es);
> +       dst_vm = aux_vm_create(false);
> +
> +       sev_mirror_create(dst_vm->fd, src_vm->fd);
> +
> +       /* Check that we can complete creation of the mirror VM.  */
> +       for (i = 0; i < NR_MIGRATE_TEST_VCPUS; ++i)
> +               vm_vcpu_add(dst_vm, i);
> +       sev_ioctl(dst_vm->fd, KVM_SEV_LAUNCH_START, &start);

I don't think this should be called on the mirror and I think it
should be an error.

In  is_cmd_allowed_from_mirror() KVM_SEV_LAUNCH_START should not be allowed:

if (cmd_id == KVM_SEV_LAUNCH_UPDATE_VMSA ||
   cmd_id == KVM_SEV_GUEST_STATUS || cmd_id == KVM_SEV_DBG_DECRYPT ||
   cmd_id == KVM_SEV_DBG_ENCRYPT)
return true;

This overrides the mirrored values and sets up the VM as a new SEV
context. I would have thought the sev_bind_asid() in
sev_launch_start() would fail because the asid is already used by the
source.

> +       if (es)
> +               sev_ioctl(dst_vm->fd, KVM_SEV_LAUNCH_UPDATE_VMSA, NULL);
> +
> +       kvm_vm_free(src_vm);
> +       kvm_vm_free(dst_vm);
> +}
> +
> +static void test_sev_mirror_parameters(void)
> +{
> +       struct kvm_vm *sev_vm, *sev_es_vm, *vm_no_vcpu, *vm_with_vcpu;
> +       int ret;
> +
> +       sev_vm = sev_vm_create(/* es= */ false);
> +       sev_es_vm = sev_vm_create(/* es= */ true);
> +       vm_with_vcpu = aux_vm_create(true);
> +       vm_no_vcpu = aux_vm_create(false);
> +
> +       ret = __sev_mirror_create(sev_vm->fd, sev_vm->fd);
> +       TEST_ASSERT(
> +               ret == -1 && errno == EINVAL,
> +               "Should not be able copy context to self. ret: %d, errno: %d\n",
> +               ret, errno);
> +
> +       ret = __sev_mirror_create(sev_vm->fd, sev_es_vm->fd);
> +       TEST_ASSERT(
> +               ret == -1 && errno == EINVAL,
> +               "Should not be able copy context to SEV enabled VM. ret: %d, errno: %d\n",
> +               ret, errno);
> +
> +       ret = __sev_mirror_create(sev_es_vm->fd, sev_vm->fd);
> +       TEST_ASSERT(
> +               ret == -1 && errno == EINVAL,
> +               "Should not be able copy context to SEV-ES enabled VM. ret: %d, errno: %d\n",
> +               ret, errno);
> +
> +       ret = __sev_mirror_create(vm_no_vcpu->fd, vm_with_vcpu->fd);
> +       TEST_ASSERT(ret == -1 && errno == EINVAL,
> +                   "Copy context requires SEV enabled. ret %d, errno: %d\n", ret,
> +                   errno);
> +
> +       ret = __sev_mirror_create(vm_with_vcpu->fd, sev_vm->fd);
> +       TEST_ASSERT(
> +               ret == -1 && errno == EINVAL,
> +               "SEV copy context requires no vCPUS on the destination. ret: %d, errno: %d\n",
> +               ret, errno);
> +
> +       kvm_vm_free(sev_vm);
> +       kvm_vm_free(sev_es_vm);
> +       kvm_vm_free(vm_with_vcpu);
> +       kvm_vm_free(vm_no_vcpu);
> +}
> +
>  int main(int argc, char *argv[])
>  {
> -       test_sev_migrate_from(/* es= */ false);
> -       test_sev_migrate_from(/* es= */ true);
> -       test_sev_migrate_locking();
> -       test_sev_migrate_parameters();
> +       if (kvm_check_cap(KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM)) {
> +               test_sev_migrate_from(/* es= */ false);
> +               test_sev_migrate_from(/* es= */ true);
> +               test_sev_migrate_locking();
> +               test_sev_migrate_parameters();
> +       }
> +       if (kvm_check_cap(KVM_CAP_VM_COPY_ENC_CONTEXT_FROM)) {
> +               test_sev_mirror(/* es= */ false);
> +               test_sev_mirror(/* es= */ true);
> +               test_sev_mirror_parameters();
> +       }
>         return 0;
>  }
> --
> 2.27.0
>
>