On Thu, Sep 05, 2024 at 12:30:07AM +0600, Dorjoy Chowdhury wrote: > On Wed, Sep 4, 2024 at 2:47 AM Dorjoy Chowdhury <dorjoychy...@gmail.com> > wrote: > > > > > > > > On Wed, Sep 4, 2024, 2:32 AM Michael S. Tsirkin <m...@redhat.com> wrote: > >> > >> On Wed, Sep 04, 2024 at 01:58:15AM +0600, Dorjoy Chowdhury wrote: > >> > On Thu, Aug 29, 2024 at 1:11 AM Michael S. Tsirkin <m...@redhat.com> > >> > wrote: > >> > > > >> > > On Thu, Aug 29, 2024 at 01:04:05AM +0600, Dorjoy Chowdhury wrote: > >> > > > On Thu, Aug 29, 2024 at 12:28 AM Michael S. Tsirkin > >> > > > <m...@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 <dorjoychy...@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! > >> > > > >> > > > >> > > Use iov_to_buf / iov_from_buf > >> > > > >> > > there are many examples in the tree, I'd look for some recent ones. > >> > > > >> > > >> > I am a bit stuck at this and I would appreciate some help. I looked at > >> > other "iov_to_buf" and "iov_from_buf" examples in QEMU and in those I > >> > see there are known request and response "structs" associated with it. > >> > But in the case of NSM, the request and responses can be arbitrary > >> > CBOR objects i.e., no specific structs or lengths associated. > >> > >> > >> take whatever you want to access, move it to a buffer with iov_to_buf > >> then access the buffer. > >> > >> reverse is even easier. put in a buffer, copy with iov_from_buf. > > > > > > I guess I will just need to copy the iov buffer (whatever the length was in > > the out_elem's out buf) to another buffer using iov_to_buf and then pass it > > to the processing function and then copy the response to the in_elem's > > buffer using iov_from_buf, right? Wouldn't the copying be redundant in this > > case as we could just instead pass the original buffers (like the iov-s are > > passed right now) to the processing function? > > > >> > >> > So I am > >> > not sure using "iov_to_buf" / "iov_from_buf" makes sense here. > >> > And about the request response being in a single s/g element, I think > >> > it's because of how the NSM driver is in drivers/misc/nsm.c (see > >> > nsm_sendrecv_msg_locked function)in the linux kernel tree. > >> > >> yes but driver is free to change this. > >> Isn't there a spec for this device to consult? > >> Sending that to virtio tc will be needed before we add this to qemu. > > > > > > I think this is the spec for this device (also mentioned in the commit > > message of this patch) > > https://lists.oasis-open.org/archives/virtio-comment/202310/msg00387.html > > > > Hi Michael. Did you get a chance to look at the NSM device spec above? > I am not sure but from the description there I think the request > response being in a single s/g element makes sense, right? > So the > current implementation of first checking out_elem with out_num == 1 > and then an in_elem with in_num == 1 should be correct. Please correct > me if I am wrong here and if I should change the implementation to > something else.
This is not what the spec says. The spec says it's a single buffer, and in virtio longo buffer can include any number of s/g elements. how many - up to driver. device does not get to decide. > > Also I had another look into using iov_to_buf and iov_from_buf. If I > wanted to use iov_to_buf here, I would just be copying the > out_elem->out_sg->iov_base to another buffer (by malloc-ing the same > length) and then passing it to the processing function > (get_nsm_request_response). And if I wanted to use the iov_from_buf > then I would probably just make another buffer the same size of > in_elem->in_sg->iov_base and then pass it to the processing function > (get_nsm_request_response). If you do not know the size, use iov_size. > The function tries to put the response > CBOR object in the response buffer but if it is too small, it then > tries to put the error response BufferTooSmall if it fails then it > returns error. I don't see how using iov_to_buf and iov_from_buf makes > any difference here other than passing in the original iov structs to > the processing function instead. Seems like doing so would just be > doing some unnecessary copying. > > Please let me know what you think so that I can better understand > this. Sorry for the back and forth a bit on this one. > > Thanks. > > Regards, > Dorjoy These are easy ways to handle arbirary s/g, but if it does not help, feel free to iterate over s/g youself.
