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

[Aneesh Kumar K.V <aneesh.kumar@kernel.org>]

Xu Yilun <yilun.xu@linux.intel.com> writes:

> 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.
>

For the current CCA implementation bind is equivalent to VDEV_CREATE
which doesn't mark the device LOCKED. Marking the device LOCKED is
driven by the guest as shown in the steps below.


>> 
>> 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?
>

I was looking at converting these numbers to strings.
"1" -> connect
"2" -> lock
"3" -> run


>
>> 
>> 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?
>

As mentioned above, them move the device to different TDISP state.

I will reply to this patch with my early RFC chnages for tsm framework.
I am not yet ready to share the CCA backend changes. But I assume having
the tsm framework changes alone can be useful?

-aneesh