vmm: parse IGVM file early and thread it through VM setup

Move IGVM file parsing from load_igvm() into a dedicated parse_igvm()
helper in igvm/mod.rs, and parse the file upfront in Vm::new() so the
resulting IgvmFile struct is available throughout VM initialization.

This is a prerequisite for extracting VMSA SEV features from the parsed
IGVM before issuing KVM_SEV_INIT2, which needs sev_features.

Signed-off-by: Ruben Hakobyan <hruben@meta.com>

vmm/src/igvm/mod.rs

@@ -27,10 +27,19 @@
 
 pub mod igvm_loader;
 mod loader;
+use std::path::Path;
+
 use igvm::snp_defs::SevVmsa;
+use igvm::{IgvmFile, IsolationType};
 use igvm_defs::IGVM_VHS_SNP_ID_BLOCK;
 use zerocopy::FromZeros;
 
+pub fn parse_igvm(igvm_path: &Path) -> Result<IgvmFile, igvm_loader::Error> {
+    let file_contents = std::fs::read(igvm_path).map_err(igvm_loader::Error::Igvm)?;
+    IgvmFile::new_from_binary(&file_contents, Some(IsolationType::Snp))
+        .map_err(igvm_loader::Error::InvalidIgvmFile)
+}
+
 #[derive(Debug, Clone)]
 pub struct IgvmLoadedInfo {
     pub gpas: Vec<u64>,