Re: [PATCH] selftests: sev_migrate_tests: Fix sev_ioctl()

[Peter Gonda]

On Tue, Dec 7, 2021 at 2:25 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Tue, Dec 07, 2021, Peter Gonda wrote:
> > TEST_ASSERT in SEV ioctl was allowing errors because it checked return
> > value was good OR the FW error code was OK. This TEST_ASSERT should
> > require both (aka. AND) values are OK. Removes the LAUNCH_START from the
> > mirror VM because this call correctly fails because mirror VMs cannot
> > call this command.
>
> This probably should be two separate patches.  First remove the bogus LAUNCH_START
> call, then fix the assert.

Thanks Sean. I'll split the patch and add your suggestion to the second one.

>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> > Cc: Marc Orr <marcorr@xxxxxxxxxx>
> > Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
> > ---
> >  tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c | 7 ++-----
> >  1 file changed, 2 insertions(+), 5 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 29b18d565cf4..8e1b1e737cb1 100644
> > --- a/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> > +++ b/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> > @@ -31,7 +31,7 @@ static void sev_ioctl(int vm_fd, int cmd_id, void *data)
> >       int ret;
> >
> >       ret = ioctl(vm_fd, KVM_MEMORY_ENCRYPT_OP, &cmd);
> > -     TEST_ASSERT((ret == 0 || cmd.error == SEV_RET_SUCCESS),
> > +     TEST_ASSERT(ret == 0 && cmd.error == SEV_RET_SUCCESS,
> >                   "%d failed: return code: %d, errno: %d, fw error: %d",
> >                   cmd_id, ret, errno, cmd.error);
>
> Hmm, reading cmd.error could also consume uninitialized data, e.g. if the ioctl()
> fails before getting into the PSP command, the error message will dump garbage.
>
> And theoretically this could get a false negative if the test stack happens to have
> '0' for cmd.error and KVM neglects to fill cmd.error when the ioctl() succeeds.
>
> So in additional to fixing the assert itself, I vote we also do:
>
> 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 29b18d565cf4..50132e165a8d 100644
> --- a/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> +++ b/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> @@ -26,6 +26,7 @@ static void sev_ioctl(int vm_fd, int cmd_id, void *data)
>         struct kvm_sev_cmd cmd = {
>                 .id = cmd_id,
>                 .data = (uint64_t)data,
> +               .error = -1u,
>                 .sev_fd = open_sev_dev_path_or_exit(),
>         };
>         int ret;

Good idea will do in the 2/2.