vmm: Add EPC device to ACPI tables

The SGX EPC region must be exposed through the ACPI tables so that the
guest can detect its presence. The guest only get the full range from
ACPI, as the specific EPC sections are directly described through the
CPUID of each vCPU.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/memory_manager.rs

@@ -1289,6 +1289,40 @@ impl Aml for MemoryManager {
             .to_aml_bytes(),
         );
 
+        #[cfg(target_arch = "x86_64")]
+        {
+            if let Some(sgx_epc_region) = &self.sgx_epc_region {
+                let min = sgx_epc_region.start().raw_value() as u64;
+                let max = min + sgx_epc_region.size() as u64 - 1;
+                // SGX EPC region
+                bytes.extend_from_slice(
+                    &aml::Device::new(
+                        "_SB_.EPC_".into(),
+                        vec![
+                            &aml::Name::new("_HID".into(), &aml::EISAName::new("INT0E0C")),
+                            // QWORD describing the EPC region start and size
+                            &aml::Name::new(
+                                "_CRS".into(),
+                                &aml::ResourceTemplate::new(vec![&aml::AddressSpace::new_memory(
+                                    aml::AddressSpaceCachable::NotCacheable,
+                                    true,
+                                    min,
+                                    max,
+                                )]),
+                            ),
+                            &aml::Method::new(
+                                "_STA".into(),
+                                0,
+                                false,
+                                vec![&aml::Return::new(&0xfu8)],
+                            ),
+                        ],
+                    )
+                    .to_aml_bytes(),
+                );
+            }
+        }
+
         bytes
     }
 }