Hypercall to let the VTL0 or VTL1 to retrieve its VMPCK so that it can communicate with the PSP

[sunilmut]

Implement the hypercall that allows the VTL0 or VTL1 retrieve the VM Platform Communication Key (VMPCK) for its own VTL, so that it can directly communicate with the PSP. The VMPCK is used to encrypt/decrypt the communication with the PSP.

[github-actions]

⚠️ Unsafe Code Detected

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[Copilot]

Pull request overview

Implements a new Hyper-V hypercall for lower VTL guests (VTL0/VTL1) to retrieve their SEV-SNP VMPCK so they can communicate directly with the PSP, and centralizes some host CPUID feature detection for OpenHCL.

Changes:

• Added HvCallGetSnpVmpck hypercall definition + output struct in hvdef and dispatch plumbing in hv1_hypercall.
• Extracted/stored VMPCKs from the SNP secrets page at partition init and exposed them via a new Underhill hypercall handler.
• Introduced openhcl_cpuid_features crate and plumbed cached CPUID features from worker startup into Hcl.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
vm/x86/x86defs/src/snp.rs	Adds SNP secrets-page VMPCK offsets/size constants.
vm/hv1/hvdef/src/lib.rs	Extends enlightenment bitfield flags; adds hypercall code + VMPCK output type/size constant.
vm/hv1/hv1_hypercall/src/imp.rs	Adds hypercall type alias + handler trait for HvGetSnpVmpck.
openhcl/virt_mshv_vtl/src/processor/snp/mod.rs	Caches VMPCK keys from secrets page and implements the new hypercall handler.
openhcl/virt_mshv_vtl/src/lib.rs	Plumbs cached CPUID features into Hcl::new on x86_64 guest builds.
openhcl/virt_mshv_vtl/Cargo.toml	Adds dependency on openhcl_cpuid_features.
openhcl/underhill_core/src/worker.rs	Initializes CPUID feature snapshot once and reuses it for MMIO-hypercall + x2APIC decisions.
openhcl/underhill_core/Cargo.toml	Swaps direct CPUID deps for openhcl_cpuid_features.
openhcl/openhcl_cpuid_features/src/lib.rs	New crate centralizing a small set of host CPUID feature queries.
openhcl/openhcl_cpuid_features/Cargo.toml	New crate manifest with x86_64-only deps.
openhcl/hcl/src/ioctl.rs	Adds CPUID feature caching to Hcl and changes Hcl::new signature on x86_64 guest builds.
openhcl/hcl/Cargo.toml	Adds openhcl_cpuid_features dependency.
Cargo.toml	Registers openhcl_cpuid_features as a workspace member dependency.
Cargo.lock	Adds lock entries for the new crate and updated dependency graph.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

[github-actions]

1 Petri tests failed (0 unstable)