On Thu, Sep 5, 2024, 2:27 AM Michael S. Tsirkin <m...@redhat.com> wrote:
> 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. > Understood. Thanks! I remember seeing other virtio device code in QEMU where only one element was popped from the queue (virtqueue_pop) and out_sg and in_sg were from that single popped element. But for NSM I saw that the first popped element didn't have any in_sg. Instead the second popped element had this. Can you give me some input on how to handle the in_sg? Right now I just assume that I need to get another element from the queue. Regards, Dorjoy
