snp: support SNP host data and guest requests

[Nikola Bojanic (nbojanic)]

Pass optional SNP host data from TTRPC to MSHV/KVM.

Handle SNP guest requests using the MSHV PSP guest request ioctl, allowing guests to retrieve attestation reports and verify the host data binding.

Builds on #4361 and #4399, which should be merged first.

[github-actions]

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[Copilot]

🟡 Changes recommended

MSHV SNP launch completion currently becomes silently idempotent, which can mask repeated/incorrect initial-page finalization and diverges from the stricter KVM SNP behavior.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR extends SEV-SNP support across the OpenVMM stack by (1) threading optional 32-byte SNP host data from the TTRPC VM service through the core config into the hypervisor backends (KVM/MSHV) and (2) adding MSHV handling for SNP guest requests (PSP guest request ioctl) so guests can fetch attestation reports and validate host-data binding. It also expands IGVM tooling/docs to cover restricted interrupt injection variants.

Changes:

• Add host_data plumbing for SNP launch-finish from TTRPC → HypervisorConfig → IGVM SNP config → MSHV/KVM launch finish.
• Implement MSHV SNP guest request handling (VMGEXIT SVM_EXITCODE_SNP_GUEST_REQUEST) and update MSHV IGVM SNP launch handling to preserve IGVM measurement order and import an IGVM-provided VMSA mapping.
• Extend IGVM generator/config/docs with restricted-injection SNP Linux-direct artifacts and update CLI/manifest docs accordingly.

File summaries

File	Description
vmm_core/virt/src/x86/snp.rs	Add reusable helpers for SNP ID block + ID auth page construction, plus unit tests.
vmm_core/virt/src/generic.rs	Extend backend-neutral SnpConfig with optional 32-byte host_data.
vmm_core/virt_mshv/src/x86_64/snp.rs	Add prepared IGVM SNP config, preserve IGVM measurement order, add VMSA mapping/import logic, add SNP guest request handling, and expand tests.
vmm_core/virt_mshv/src/x86_64/mod.rs	Teach MSHV proto-partition build to pre-parse IGVM SNP config before partition build and carry it through isolation setup.
vmm_core/virt_mshv/src/lib.rs	Store proto-partition isolation state (including optional IGVM SNP config) instead of a single SNP CPUID-offload flag.
vmm_core/virt_kvm/src/snp.rs	Pass optional host_data into KVM_SEV_SNP_LAUNCH_FINISH; update SNP config test helper.
vm/x86/x86defs/src/snp.rs	Define zerocopy-friendly structs for the SNP PSP ID auth (ID_AUTH) page with size assertion.
vm/loader/manifests/snp-linux-direct-restricted.json	Add a restricted-injection SNP Linux-direct manifest profile (intended for MSHV bring-up).
vm/loader/manifests/README.md	Document normal vs restricted injection outputs and update example invocation.
vm/loader/igvmfilegen/src/snp_linux_direct.rs	Parameterize injection mode and ensure generated VMSA reflects normal vs restricted injection; add test.
vm/loader/igvmfilegen/src/main.rs	Allow snp_linux_direct IGVM generation with restricted injection mode (remove prior restriction).
vm/loader/igvmfilegen_config/src/lib.rs	Add config test coverage for parsing the new restricted SNP Linux-direct manifest.
petri/src/vm/openvmm/construct.rs	Initialize new HypervisorConfig::snp_host_data field in Petri config construction.
openvmm/openvmm_ttrpc_vmservice/src/vmservice.proto	Add IGVM boot option and IsolationConfig (including optional SNP host data) to the VM service API.
openvmm/openvmm_entry/src/ttrpc/mod.rs	Parse isolation + host data from TTRPC requests, enforce SNP+IGVM constraints, and populate HypervisorConfig.
openvmm/openvmm_entry/src/lib.rs	Initialize HypervisorConfig::snp_host_data for CLI-created configs.
openvmm/openvmm_defs/src/config.rs	Add HypervisorConfig::snp_host_data: Option<[u8; 32]>.
openvmm/openvmm_core/src/worker/vm_loaders/igvm.rs	Build SNP isolation config from IGVM metadata plus optional host-provided host data.
openvmm/openvmm_core/src/worker/dispatch.rs	Thread host data into IGVM SNP config build; relax a KVM SNP guest_memfd constraint around with_hv.
Guide/src/reference/openvmm/management/cli.md	Update SNP CLI documentation to include IGVM boot support details and a minimal MSHV IGVM example.

Review details

Suppressed comments (1)

vmm_core/virt_mshv/src/x86_64/snp.rs:703

• Returning Ok(()) when the SNP launch state is already Finished can mask a real loader bug: a second accept_initial_pages call with non-empty pages would be silently ignored. It’s safer (and consistent with the KVM SNP path) to return an explicit error when the launch is already complete.

            match *state {
                SnpLaunchState::NotStarted => *state = SnpLaunchState::Started,
                SnpLaunchState::Started => return Err(SnpError::LaunchInProgress.into()),
                SnpLaunchState::Finished => return Ok(()),
                SnpLaunchState::Failed => return Err(SnpError::LaunchFailed.into()),

• Files reviewed: 20/20 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🟡 Changes recommended

It introduces a MeshPayload wire-compatibility risk in HypervisorConfig field ordering and needs stricter GHCB field validation in the new MSHV SNP guest-request handler.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 10/10 changed files
• Comments generated: 2
• Review effort level: Lite