Add various helper function required by SEV-SNP guest

mshv-bindings/src/snp.rs

@@ -16,6 +16,9 @@
     non_upper_case_globals
 )]
 use crate::bindings::*;
+use vmm_sys_util::errno;
+
+type Result<T> = std::result::Result<T, errno::Error>;
 
 pub const GHCB_PROTOCOL_VERSION_MIN: u32 = 1;
 pub const GHCB_PROTOCOL_VERSION_MAX: u32 = 2;
@@ -658,3 +661,59 @@ pub fn get_default_vmgexit_offload_features() -> hv_sev_vmgexit_offload {
 
     offload_feature
 }
+
+///
+/// Helper function to parse the GPA range
+///
+pub fn parse_gpa_range(range: hv_gpa_page_range) -> Result<(u64, u64)> {
+    let gpa_page_start;
+    let gpa_page_count;
+
+    // SAFETY: access union field
+    unsafe {
+        if range.page.largepage() > 0 {
+            return Err(errno::Error::new(libc::EINVAL));
+        } else {
+            gpa_page_start = range.page.basepfn();
+            gpa_page_count = 1 + range.page.additional_pages();
+        }
+    }
+    Ok((gpa_page_start, gpa_page_count))
+}
+
+///
+/// Get default SEV-SNP guest policy supported by
+/// Microsoft Hypervisor.
+///
+pub fn get_default_snp_guest_policy() -> hv_snp_guest_policy {
+    let mut snp_policy = hv_snp_guest_policy { as_uint64: 0_u64 };
+
+    // SAFETY: access union field
+    unsafe {
+        snp_policy.__bindgen_anon_1.set_minor_version(0x1f);
+        snp_policy.__bindgen_anon_1.set_major_version(0x00);
+        snp_policy.__bindgen_anon_1.set_smt_allowed(1);
+        snp_policy.__bindgen_anon_1.set_vmpls_required(1);
+        snp_policy.__bindgen_anon_1.set_migration_agent_allowed(0);
+        snp_policy.__bindgen_anon_1.set_debug_allowed(0);
+    }
+
+    snp_policy
+}
+
+///
+/// Helper function to get sev control register
+/// for a given VMSA PFN.
+///
+pub fn get_sev_control_register(vmsa_pfn: u64) -> u64 {
+    let mut sev_control = hv_x64_register_sev_control { as_uint64: 0_u64 };
+
+    // SAFETY: access union field
+    unsafe {
+        sev_control.__bindgen_anon_1.set_enable_encrypted_state(1);
+        sev_control
+            .__bindgen_anon_1
+            .set_vmsa_gpa_page_number(vmsa_pfn);
+        sev_control.as_uint64
+    }
+}