linux-kernel - Re: [PATCH 3/3] selftests: sev_migrate

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Date:   Thu, 9 Dec 2021 12:45:49 -0800
From:   Marc Orr <marcorr@...gle.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH 3/3] selftests: sev_migrate_tests: Add mirror command tests

On Wed, Dec 8, 2021 at 9:53 PM Marc Orr <marcorr@...gle.com> wrote:
>
> On Wed, Dec 8, 2021 at 11:16 AM Peter Gonda <pgonda@...gle.com> wrote:
> >
> > Add tests to confirm mirror vms can only run correct subset of commands.
> >
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Sean Christopherson <seanjc@...gle.com>
> > Cc: Marc Orr <marcorr@...gle.com>
> > Signed-off-by: Peter Gonda <pgonda@...gle.com>
> > ---
> >  .../selftests/kvm/x86_64/sev_migrate_tests.c  | 55 +++++++++++++++++--
> >  1 file changed, 51 insertions(+), 4 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 4bb960ca6486..80056bbbb003 100644
> > --- a/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> > +++ b/tools/testing/selftests/kvm/x86_64/sev_migrate_tests.c
> > @@ -21,7 +21,7 @@
> >  #define NR_LOCK_TESTING_THREADS 3
> >  #define NR_LOCK_TESTING_ITERATIONS 10000
> >
> > -static void sev_ioctl(int vm_fd, int cmd_id, void *data)
> > +static int __sev_ioctl(int vm_fd, int cmd_id, void *data, __u32 *fw_error)
> >  {
> >         struct kvm_sev_cmd cmd = {
> >                 .id = cmd_id,
> > @@ -30,11 +30,20 @@ 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,
> > +       *fw_error = cmd.error;
> > +       return ret;
> > +}
> > +
> > +static void sev_ioctl(int vm_fd, int cmd_id, void *data)
> > +{
> > +       int ret;
> > +       __u32 fw_error;
> > +
> > +       ret = __sev_ioctl(vm_fd, cmd_id, data, &fw_error);
> > +       TEST_ASSERT(ret == 0 && fw_error == SEV_RET_SUCCESS,
> >                     "%d failed: return code: %d, errno: %d, fw error: %d",
> > -                   cmd_id, ret, errno, cmd.error);
> > +                   cmd_id, ret, errno, fw_error);
> >  }
> >
> >  static struct kvm_vm *sev_vm_create(bool es)
> > @@ -226,6 +235,42 @@ static void sev_mirror_create(int dst_fd, int src_fd)
> >         TEST_ASSERT(!ret, "Copying context failed, ret: %d, errno: %d\n", ret, errno);
> >  }
> >
> > +static void verify_mirror_allowed_cmds(int vm_fd)
> > +{
> > +       struct kvm_sev_guest_status status;
> > +
> > +       for (int cmd_id = KVM_SEV_INIT; cmd_id < KVM_SEV_NR_MAX; ++cmd_id) {
> > +               int ret;
> > +               __u32 fw_error;
> > +
> > +               /*
> > +                * These commands are allowed for mirror VMs, all others are
> > +                * not.
> > +                */
> > +               switch (cmd_id) {
> > +               case KVM_SEV_LAUNCH_UPDATE_VMSA:
> > +               case KVM_SEV_GUEST_STATUS:
> > +               case KVM_SEV_DBG_DECRYPT:
> > +               case KVM_SEV_DBG_ENCRYPT:
> > +                       continue;
> > +               default:
> > +                       break;
> > +               }
> > +
> > +               /*
> > +                * These commands should be disallowed before the data
> > +                * parameter is examined so NULL is OK here.
> > +                */
> > +               ret = __sev_ioctl(vm_fd, cmd_id, NULL, &fw_error);
> > +               TEST_ASSERT(
> > +                       ret == -1 && errno == EINVAL,
> > +                       "Should not be able call command: %d. ret: %d, errno: %d\n",
> > +                       cmd_id, ret, errno);
> > +       }
> > +
> > +       sev_ioctl(vm_fd, KVM_SEV_GUEST_STATUS, &status);
>
> Why is this here? I'd either delete it or maybe alternatively move it
> into the `case KVM_SEV_GUEST_STATUS` with a corresponding TEST_ASSERT
> to check that the command succeeded. Something like:
>
> ...
>                switch (cmd_id) {
>                case KVM_SEV_GUEST_STATUS:
>                     sev_ioctl(vm_fd, KVM_SEV_GUEST_STATUS, &status);
>                     TEST_ASSERT(ret == 0 && fw_error == SEV_RET_SUCCESS, ...);
>                     continue;
>                case KVM_SEV_LAUNCH_UPDATE_VMSA:
>                case KVM_SEV_DBG_DECRYPT:
>                case KVM_SEV_DBG_ENCRYPT:
>                        continue;
>                default:
>                        break;
>                }

For posterity: Peter pointed out to me offline that `sev_ioctl()` in
fact does the TEST_ASSERT internally. Doh! So this line is fine as is.