acpi_spec: add MCFG definitions and parsing #1985
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Pull Request Overview
This PR adds MCFG (Memory Mapped Configuration) table definitions and parsing to the acpi_spec crate. The MCFG table describes memory-mapped configuration space base addresses for PCIe root complex devices, enabling Enhanced Configuration Access Mechanism (ECAM) support.
Key changes:
- Adds complete MCFG table structure definitions with proper zerocopy traits
- Implements parsing functionality with comprehensive error handling
- Provides both borrowed and owned parsing variants for different use cases
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| vm/acpi_spec/src/mcfg.rs | New module implementing MCFG table structures, parsing logic, and error handling |
| vm/acpi_spec/src/lib.rs | Exports the new mcfg module |
| pub struct McfgSegmentBusRange { | ||
| pub ecam_base: u64_ne, | ||
| pub segment: u16_ne, | ||
| pub start_bus: u8, | ||
| pub end_bus: u8, | ||
| pub rsvd: u32_ne, | ||
| } |
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This can be a bitfield(u128), and then you're guaranteed that the size will be correct.
In general, I prefer bitfields for structures that are up to 128 bits in length that need to match some hardware spec. That is perhaps stylistic without any real basis. Interested what you / others think.
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Personally, I think using a bitfield to represent a structure where all members are on byte boundaries is confusing, so I would lean towards keeping it as-is with the const assert. However, I am still in the process of refining my personal stylistic preferences in Rust
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my rule of thumb is generally to use bitfields if there are actual bit fields, but if all members are standard integers then it's not usually something I use. I don't think we codify that anywhere, but regardless as long as you assert the size correctly I don't think either approach is wrong.
jackschefer-msft
assigned
jackschefer-msft and
chris-oo and unassigned
jackschefer-msft
This change adds currently unused MCFG definitions and parsing to the `acpi_spec` crate. The MCFG table describes the memory-mapped configuration space base address for each PCIe root complex device on a system. Future changes will actually utilize these MCFG definitions to expose enhanced configuration access mechanism (ECAM) addresses to guests. See microsoft#1976 for a preview.
4 participants
This change adds currently unused MCFG definitions and parsing to the
acpi_speccrate. The MCFG table describes the memory-mapped configuration space base address for each PCIe root complex device on a system.Future changes will actually utilize these MCFG definitions to expose enhanced configuration access mechanism (ECAM) addresses to guests. See #1976 for a preview.