Re: [PATCH 05/11] PCI/TSM: Authenticate devices via platform TSM

[Xu Yilun <yilun.xu@linux.intel.com>]

On Fri, Feb 21, 2025 at 01:43:28PM +0530, Aneesh Kumar K.V wrote:
> Alexey Kardashevskiy <aik@amd.com> writes:
> 
> ....
> 
> >
> > I am trying to wrap my head around your tsm. here is what I got in my tree:
> > https://github.com/aik/linux/blob/tsm/include/linux/tsm.h
> >
> > Shortly:
> >
> > drivers/virt/coco/tsm.ko does sysfs (including "connect" and "bind" to 
> > control and "certs"/"report" to attest) and implements tsm_dev/tsm_tdi, 
> > it does not know pci_dev;
> >
> > drivers/pci/tsm-pci.ko creates/destroys tsm_dev/tsm_dev using tsm.ko;
> >
> > drivers/crypto/ccp/ccp.ko (the PSP guy) registers:
> > - tsm_subsys in tsm.ko (which does "connect" and "bind" and
> > - tsm_bus_subsys in tsm-pci.ko (which does "spdm_forward")
> > ccp.ko knows about pci_dev and whatever else comes in the future, and 
> > ccp.ko's "connect" implementation calls the IDE library (I am adopting 
> > yours now, with some tweaks).
> >
> > tsm-dev and tsm-tdi embed struct dev each and are added as children to 
> > PCI devices: no hide/show attrs, no additional TSM pointer in struct 
> > device or pci_dev, looks like:
> >
> > aik@sc ~> ls  /sys/bus/pci/devices/0000:e1:04.0/tsm-tdi/tdi:0000:e1:04.0/
> > device  power  subsystem  tsm_report  tsm_report_user  tsm_tdi_bind 
> > tsm_tdi_status  tsm_tdi_status_user  uevent
> >
> > aik@sc ~> ls  /sys/bus/pci/devices/0000:e1:04.0/tsm_dev/
> > device  power  subsystem  tsm_certs  tsm_cert_slot  tsm_certs_user 
> > tsm_dev_connect  tsm_dev_status  tsm_meas  tsm_meas_user  uevent
> >
> > aik@sc ~> ls /sys/class/tsm/tsm0/
> > device  power  stream0:0000:e1:00.0  subsystem  uevent
> >
> > aik@sc ~> ls /sys/class/tsm-dev/
> > tdev:0000:c0:01.1  tdev:0000:e0:01.1  tdev:0000:e1:00.0
> >
> > aik@sc ~> ls /sys/class/tsm-tdi/
> > tdi:0000:c0:01.1  tdi:0000:e0:01.1  tdi:0000:e1:00.0  tdi:0000:e1:04.0 
> > tdi:0000:e1:04.1  tdi:0000:e1:04.2  tdi:0000:e1:04.3
> >
> >
> > SPDM forwarding seems a bus-agnostic concept, "connect" is a PCI thing 
> > but pci_dev is only needed for DOE/IDE.
> >
> > Or is separating struct pci_dev from struct device not worth it and most 
> > of it should go to tsm-pci.ko? Then what is left for tsm.ko? Thanks,
> >
> 
> For the Arm CCA DA, I have structured the flow as follows. I am
> currently refining my changes to prepare them for posting. I am using
> tsm-core in both the host and guest. There is no bind interface at the
> sysfs level; instead, it is managed via the KVM ioctl
> 
> Host:
> step 1.
> echo ${DEVICE} > /sys/bus/pci/devices/${DEVICE}/driver/unbind
> echo vfio-pci > /sys/bus/pci/devices/${DEVICE}/driver_override
> echo ${DEVICE} > /sys/bus/pci/drivers_probe
> 
> step 2.
> echo 1 > /sys/bus/pci/devices/$DEVICE/tsm/connect
> 
> step 3.
> using VMM to make the new KVM_SET_DEVICE_ATTR ioctl
> 
> +		dev_num = vfio_devices[i].dev_hdr.dev_num;
> +		/* kvmtool only do 0 domain, 0 bus and 0 function devices. */
> +		guest_bdf = (0ULL << 32) | (0 << 16) | dev_num << 11 | (0 << 8);
> +
> +		struct kvm_vfio_tsm_bind param = {
> +			.guest_rid = guest_bdf,
> +			.devfd = vfio_devices[i].fd,
> +		};
> +		struct kvm_device_attr attr = {
> +			.group = KVM_DEV_VFIO_DEVICE,
> +			.attr = KVM_DEV_VFIO_DEVICE_TDI_BIND,
> +			.addr = (__u64)&param,
> +		};
> +
> +		if (ioctl(kvm_vfio_device, KVM_SET_DEVICE_ATTR, &attr)) {
> +			pr_err("Failed KVM_SET_DEVICE_ATTR for KVM_DEV_VFIO_DEVICE");
> +			return -ENODEV;
> +		}
> +

I think bind (which brings device to a LOCKED state, no MMIO, no DMA)
cannot be a driver agnostic behavior. So I think it should be a VFIO
ioctl.

> 
> Now in the guest we follow the below steps
> 
> step 1:
> echo ${DEVICE} > /sys/bus/pci/devices/${DEVICE}/driver/unbind
> 
> step 2: Move the device to TDISP LOCK state
> echo 1 > /sys/bus/pci/devices/0000:00:00.0/tsm/connect
> echo 3 > /sys/bus/pci/devices/0000:00:00.0/tsm/connect

Reuse the 'connect' interface? I think it conceptually brings chaos. Is
it better we create a new interface?

> 
> step 3: Moves the device to TDISP RUN state
> echo 4 > /sys/bus/pci/devices/0000:00:00.0/tsm/connect

Could you elaborate what '1'/'3'/'4' stand for?

Thanks,
Yilun

> 
> step 4: Load the driver again.
> echo ${DEVICE} > /sys/bus/pci/drivers_probe
> 
>