ext/pci: fix crash on devices with non-standard PCI segment

[bartlomiejkida]

Summary
On Dell Latitude 5420 (and likely other Tiger Lake laptops), Intel VMD (Volume Management Device) is enabled by default in BIOS. VMD creates a virtual PCI segment 10000: for the storage devices it manages:

10000:e0:17.0 SATA controller: Intel Corporation Tiger Lake-LP SATA Controller (rev 20)
10000:e0:1d.0 PCI bridge: Intel Corporation Tiger Lake-LP PCI Express Root Port #9 (rev 20)

When qubesd enumerates PCI devices, sbdf_to_path() hits an AssertionError on these devices because their bus topology doesn't match the expected hierarchy. This crashes the entire admin.vm.device.pci.Available API call, making qvm-pci unusable.

Full lspci on this machine:

[root@dom0 ~]# lspci
0000:00:00.0 Host bridge: Intel Corporation Tiger Lake-UP3/H35 4 cores Host Bridge/DRAM Registers (rev 01)
0000:00:02.0 VGA compatible controller: Intel Corporation TigerLake-LP GT2 [Iris Xe Graphics] (rev 01)
0000:00:04.0 Signal processing controller: Intel Corporation TigerLake-LP Dynamic Tuning Processor Participant (rev 01)
0000:00:07.0 PCI bridge: Intel Corporation Tiger Lake-LP Thunderbolt 4 PCI Express Root Port #0 (rev 01)
0000:00:07.1 PCI bridge: Intel Corporation Tiger Lake-LP Thunderbolt 4 PCI Express Root Port #1 (rev 01)
0000:00:0d.0 USB controller: Intel Corporation Tiger Lake-LP Thunderbolt 4 USB Controller (rev 01)
0000:00:0d.2 USB controller: Intel Corporation Tiger Lake-LP Thunderbolt 4 NHI #0 (rev 01)
0000:00:0e.0 RAID bus controller: Intel Corporation Volume Management Device NVMe RAID Controller
0000:00:12.0 Serial controller: Intel Corporation Tiger Lake-LP Integrated Sensor Hub (rev 20)
0000:00:14.0 USB controller: Intel Corporation Tiger Lake-LP USB 3.2 Gen 2x1 xHCI Host Controller (rev 20)
0000:00:14.2 RAM memory: Intel Corporation Tiger Lake-LP Shared SRAM (rev 20)
0000:00:14.3 Network controller: Intel Corporation Wi-Fi 6 AX201 (rev 20)
0000:00:15.0 Serial bus controller: Intel Corporation Tiger Lake-LP Serial IO I2C Controller #0 (rev 20)
0000:00:15.1 Serial bus controller: Intel Corporation Tiger Lake-LP Serial IO I2C Controller #1 (rev 20)
0000:00:16.0 Communication controller: Intel Corporation Tiger Lake-LP Management Engine Interface (rev 20)
0000:00:16.3 Serial controller: Intel Corporation Tiger Lake-LP Active Management Technology - SOL (rev 20)
0000:00:17.0 System peripheral: Intel Corporation RST VMD Managed Controller
0000:00:1c.0 PCI bridge: Intel Corporation Tiger Lake-LP PCI Express Root Port #7 (rev 20)
0000:00:1d.0 System peripheral: Intel Corporation RST VMD Managed Controller
0000:00:1f.0 ISA bridge: Intel Corporation Tiger Lake-LP LPC Controller (rev 20)
0000:00:1f.3 Audio device: Intel Corporation Tiger Lake-LP Smart Sound Technology Audio Controller (rev 20)
0000:00:1f.4 SMBus: Intel Corporation Tiger Lake-LP SMBus Controller (rev 20)
0000:00:1f.5 Serial bus controller: Intel Corporation Tiger Lake-LP SPI Controller (rev 20)
0000:00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (13) I219-LM (rev 20)
0000:01:00.0 PCI bridge: Intel Corporation JHL7440 Thunderbolt 3 Bridge [Titan Ridge DD 2018] (rev 06)
0000:02:02.0 PCI bridge: Intel Corporation JHL7440 Thunderbolt 3 Bridge [Titan Ridge DD 2018] (rev 06)
0000:02:04.0 PCI bridge: Intel Corporation JHL7440 Thunderbolt 3 Bridge [Titan Ridge DD 2018] (rev 06)
0000:03:00.0 USB controller: Intel Corporation JHL7440 Thunderbolt 3 USB Controller [Titan Ridge DD 2018] (rev 06)
0000:71:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
10000:e0:17.0 SATA controller: Intel Corporation Tiger Lake-LP SATA Controller (rev 20)
10000:e0:1d.0 PCI bridge: Intel Corporation Tiger Lake-LP PCI Express Root Port #9 (rev 20)
10000:e1:00.0 Non-Volatile memory controller: Sandisk Corp IX SN530 NVMe SSD / microSD Express Card (DRAM-less) (rev 01)

Fix
Catch the AssertionError from sbdf_to_path() in PCIDevice.init and convert it to UnsupportedDevice. The existing handler in on_device_list_pci already skips unsupported devices gracefully with a warning log. VMD-managed devices cannot be passed through to VMs via standard PCI passthrough anyway, so skipping them is the correct behavior.

This patch fixes qvm-pci, but also qubes-global-config, which needs to load the PCI device list first.

Closes QubesOS/qubes-issues#10847

[ben-grande]

PipelineRetryFailed

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.11%. Comparing base (2488f2b) to head (db3fb63).

Files with missing lines	Patch %	Lines
qubes/ext/pci.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #802      +/-   ##
==========================================
- Coverage   70.12%   70.11%   -0.01%     
==========================================
  Files          61       61              
  Lines       14001    14004       +3     
==========================================
+ Hits         9818     9819       +1     
- Misses       4183     4185       +2     

Flag	Coverage Δ
unittests	70.11% <50.00%> (-0.01%)	⬇️

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[marmarek]

I don't like catching AssertionError here. Asserts should never trigger - if they do, it means a but somewhere (might be also in the assert condition itself).

But also, shouldn't the VMD case be handled by the regex match above already? It has 4 hex digits for segment, but VMD devices have 5, so it shouldn't match there.

[marmarek]

virsh -c xen nodedev-list output in dom0 might be useful to see what happened here.