vmm: acpi: Mark non-boot vCPUs as disabled in the MADT table

The MADT table contains the details of all the potential vCPUs and
whether they are present at boot (as indicated by the flags field.)

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/acpi.rs

@@ -355,9 +355,11 @@ pub fn create_dsdt_table(
 
     dsdt
 }
+
 pub fn create_acpi_tables(
     guest_mem: &GuestMemoryMmap,
-    num_cpus: u8,
+    boot_vcpus: u8,
+    max_vcpus: u8,
     serial_enabled: bool,
     start_of_device_area: GuestAddress,
     end_of_device_area: GuestAddress,
@@ -372,7 +374,7 @@ pub fn create_acpi_tables(
         serial_enabled,
         start_of_device_area,
         end_of_device_area,
-        num_cpus,
+        boot_vcpus,
     );
     let dsdt_offset = rsdp_offset.checked_add(RSDP::len() as u64).unwrap();
     guest_mem
@@ -413,13 +415,20 @@ pub fn create_acpi_tables(
     let mut madt = SDT::new(*b"APIC", 44, 5, *b"CLOUDH", *b"CHMADT  ", 1);
     madt.write(36, layout::APIC_START);
 
-    for cpu in 0..num_cpus {
+    // This is also checked in the commandline parsing.
+    assert!(boot_vcpus <= max_vcpus);
+
+    for cpu in 0..max_vcpus {
         let lapic = LocalAPIC {
             r#type: 0,
             length: 8,
             processor_id: cpu,
             apic_id: cpu,
-            flags: 1 << MADT_CPU_ENABLE_FLAG,
+            flags: if cpu < boot_vcpus {
+                1 << MADT_CPU_ENABLE_FLAG
+            } else {
+                0
+            },
         };
         madt.append(lapic);
     }

vmm/src/vm.rs

@@ -513,6 +513,7 @@ impl Vm {
         )
         .map_err(|_| Error::CmdLine)?;
         let boot_vcpus = self.cpu_manager.lock().unwrap().boot_vcpus();
+        let max_vcpus = self.cpu_manager.lock().unwrap().max_vcpus();
 
         #[allow(unused_mut, unused_assignments)]
         let mut rsdp_addr: Option<GuestAddress> = None;
@@ -533,6 +534,7 @@ impl Vm {
                 crate::acpi::create_acpi_tables(
                     &mem,
                     boot_vcpus,
+                    max_vcpus,
                     self.config.serial.mode != ConsoleOutputMode::Off,
                     start_of_device_area,
                     end_of_range,