vm/devices/vpci: track vtom and register for mmio with vtom (#2306) #2315
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…t#2306) On hardware isolated guests with vtom, the guest may access vpci config space with vtom set. Add this tracking in vpci and register for mmio with vtom, so we can correctly handle guest accesses on SNP & TDX. This fixes vpci relay on TDX, as both Linux and Windows will access config space with vtom set.
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Pull Request Overview
This PR adds support for vtom (Virtual Trust Boundary On Memory) to the VPCI device infrastructure. The vtom is a memory bit used in hardware-isolated VMs to distinguish between shared and private memory regions. The PR threads the vtom parameter through the VPCI device creation and initialization paths to enable proper MMIO address handling when vtom is enabled.
Key changes:
- Added
vtom: Option<u64>parameter to VPCI device creation functions - Implemented vtom bit stripping logic in MMIO read/write handlers to normalize addresses
- Created separate MMIO regions for vtom-enabled and non-vtom config space access
Reviewed Changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| vmm_core/src/device_builder.rs | Threads vtom parameter through to VpciBus::new |
| vm/devices/pci/vpci_relay/src/lib.rs | Adds vtom field to VpciRelay and passes it through device creation |
| vm/devices/pci/vpci_client/src/tests.rs | Updates test to pass None for vtom parameter |
| vm/devices/pci/vpci/src/device.rs | Adds VpciConfigSpaceVtom struct and vtom handling in map/unmap operations |
| vm/devices/pci/vpci/src/bus.rs | Implements vtom bit stripping in MMIO handlers and adds vtom tracking |
| openvmm/hvlite_core/src/worker/dispatch.rs | Passes None for vtom in non-isolated VM contexts |
| openhcl/underhill_core/src/worker.rs | Passes vtom value from configuration to VPCI devices |
mebersol
approved these changes
Oct 30, 2025
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On hardware isolated guests with vtom, the guest may access vpci config space with vtom set. Add this tracking in vpci and register for mmio with vtom, so we can correctly handle guest accesses on SNP & TDX.
This fixes vpci relay on TDX, as both Linux and Windows will access config space with vtom set.
Fixup of a cherry pick from #2306 (required changes in device_builder.rs)