Re: [PATCH v5 5/8] device/virtio-nsm: Support for Nitro Secure Module device

[Dorjoy Chowdhury]

On Thu, Aug 29, 2024 at 12:28 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, Aug 22, 2024 at 09:08:46PM +0600, Dorjoy Chowdhury wrote:
> > Nitro Secure Module (NSM)[1] device is used in AWS Nitro Enclaves[2]
> > for stripped down TPM functionality like cryptographic attestation.
> > The requests to and responses from NSM device are CBOR[3] encoded.
> >
> > This commit adds support for NSM device in QEMU. Although related to
> > AWS Nitro Enclaves, the virito-nsm device is independent and can be
> > used in other machine types as well. The libcbor[4] library has been
> > used for the CBOR encoding and decoding functionalities.
> >
> > [1] 
> > https://lists.oasis-open.org/archives/virtio-comment/202310/msg00387.html
> > [2] https://docs.aws.amazon.com/enclaves/latest/user/nitro-enclave.html
> > [3] http://cbor.io/
> > [4] https://libcbor.readthedocs.io/en/latest/
> >
> > Signed-off-by: Dorjoy Chowdhury <dorjoychy111@gmail.com>
> > ---
> >  MAINTAINERS                      |   10 +
> >  hw/virtio/Kconfig                |    5 +
> >  hw/virtio/cbor-helpers.c         |  326 ++++++
> >  hw/virtio/meson.build            |    6 +
> >  hw/virtio/virtio-nsm-pci.c       |   73 ++
> >  hw/virtio/virtio-nsm.c           | 1638 ++++++++++++++++++++++++++++++
> >  include/hw/virtio/cbor-helpers.h |   46 +
> >  include/hw/virtio/virtio-nsm.h   |   59 ++
> >  meson.build                      |    2 +
> >  9 files changed, 2165 insertions(+)

[...]

> > +static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
> > +{
> > +    g_autofree VirtQueueElement *out_elem = NULL;
> > +    g_autofree VirtQueueElement *in_elem = NULL;
> > +    VirtIONSM *vnsm = VIRTIO_NSM(vdev);
> > +    Error *err = NULL;
> > +
> > +    out_elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> > +    if (!out_elem) {
> > +        /* nothing in virtqueue */
> > +        return;
> > +    }
> > +
> > +    if (out_elem->out_num != 1) {
> > +        virtio_error(vdev, "Expected one request buffer first in 
> > virtqueue");
> > +        goto cleanup;
> > +    }
>
> Seems to assume request in a single s/g element?
> We generally avoid this kind of thing.
>
> Applies equally elsewheree.
>

Thank you for reviewing. I think I did it this way (first virqueue_pop
gives out_elem with out_num == 1 and the next virtqueue_pop gives
in_elem with in_num == 1) after seeing what the virqueue contains
(using printfs) when running in a VM and sending some NSM requests and
I noticed the above. Can you give me a bit more details about what
this should be like? Is there any existing virtio device code I can
look at for example?
Thanks!

> > +
> > +    in_elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> > +    if (!in_elem) {
> > +        virtio_error(vdev, "Expected response buffer after request buffer "
> > +                     "in virtqueue");
> > +        goto cleanup;
> > +    }
> > +    if (in_elem->in_num != 1) {
> > +        virtio_error(vdev, "Expected one response buffer after request 
> > buffer "
> > +                     "in virtqueue");
> > +        goto cleanup;
> > +    }
> > +
> > +    if (!get_nsm_request_response(vnsm, out_elem->out_sg, in_elem->in_sg,
> > +                                  &err)) {
> > +        error_report_err(err);
> > +        virtio_error(vdev, "Failed to get NSM request response");
> > +        goto cleanup;
> > +    }
> > +
> > +    virtqueue_push(vq, out_elem, 0);
> > +    virtqueue_push(vq, in_elem, in_elem->in_sg->iov_len);
> > +    virtio_notify(vdev, vq);
> > +    return;
> > +
> > + cleanup:
> > +    if (out_elem) {
> > +        virtqueue_detach_element(vq, out_elem, 0);
> > +    }
> > +    if (in_elem) {
> > +        virtqueue_detach_element(vq, in_elem, 0);
> > +    }
> > +    return;
> > +}
> > +
> > +static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
> > +{
> > +    return f;
> > +}
> > +

[...]

Regards,
Dorjoy