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

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

On Wed, Feb 26, 2025 at 05:40:02PM +0530, Aneesh Kumar K.V wrote:
> 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.

Could you elaborate why vdev create & LOCK can't be done at the same
time, when guest requests "lock"? Intel TDX also requires firmware calls
like tdi_create(alloc metadata) & tdi_bind(do LOCK), but I don't see
there is need to break them out in different phases.

> 
> 
> >> 
> >> 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

What does "connect" do in guest?

Thanks,
Yilun

> "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