Add new online capable vCPUs sockets to MADT

Extend the MADT to contain MAX_SUPPORTED_VCPUS (32) entries. Only the
number specified in the machine_config are enabled. The rest are "online
capable", meaning they can be brought online.

Signed-off-by: James Curtis <jxcurtis@amazon.co.uk>

Author: JamesC1305

src/acpi-tables/src/madt.rs

@@ -13,6 +13,7 @@ use crate::{checksum, AcpiError, Result, Sdt, SdtHeader};
 
 const MADT_CPU_ENABLE_FLAG: u32 = 0;
 
+const MADT_CPU_ONLINE_CAPABLE_FLAG: u32 = 1;
 // clippy doesn't understand that we actually "use" the fields of this struct when we serialize
 // them as bytes in guest memory, so here we just ignore dead code to avoid having to name
 // everything with an underscore prefix
@@ -28,13 +29,18 @@ pub struct LocalAPIC {
 }
 
 impl LocalAPIC {
-    pub fn new(cpu_id: u8) -> Self {
+    pub fn new(cpu_id: u8, online: bool) -> Self {
+        let flags = if online {
+            U32::new(1u32 << MADT_CPU_ENABLE_FLAG)
+        } else {
+            U32::new(1u32 << MADT_CPU_ONLINE_CAPABLE_FLAG)
+        };
         Self {
             r#type: 0,
             length: 8,
             processor_uid: cpu_id,
             apic_id: cpu_id,
-            flags: U32::new(1u32 << MADT_CPU_ENABLE_FLAG),
+            flags,
         }
     }
 }
@@ -140,3 +146,30 @@ impl Sdt for Madt {
         Ok(())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use zerocopy::little_endian::U32;
+
+    use crate::madt::LocalAPIC;
+
+    #[test]
+    fn test_online_local_apic() {
+        let online_apic = super::LocalAPIC::new(0, true);
+        assert_eq!(online_apic.r#type, 0);
+        assert_eq!(online_apic.length, 8);
+        assert_eq!(online_apic.processor_uid, 0);
+        assert_eq!(online_apic.apic_id, 0);
+        assert_eq!(online_apic.flags, U32::new(1));
+    }
+
+    #[test]
+    fn test_online_capable_local_apic() {
+        let online_capable_apic = LocalAPIC::new(1, false);
+        assert_eq!(online_capable_apic.r#type, 0);
+        assert_eq!(online_capable_apic.length, 8);
+        assert_eq!(online_capable_apic.processor_uid, 1);
+        assert_eq!(online_capable_apic.apic_id, 1);
+        assert_eq!(online_capable_apic.flags, U32::new(2));
+    }
+}

src/vmm/src/acpi/x86_64.rs

@@ -14,15 +14,21 @@ use zerocopy::AsBytes;
 
 use crate::arch::x86_64::layout;
 use crate::device_manager::legacy::PortIODeviceManager;
+use crate::vmm_config::machine_config::MAX_SUPPORTED_VCPUS;
 
 #[inline(always)]
 pub(crate) fn setup_interrupt_controllers(nr_vcpus: u8) -> Vec<u8> {
-    let mut ic =
-        Vec::with_capacity(size_of::<IoAPIC>() + (nr_vcpus as usize) * size_of::<LocalAPIC>());
+    let mut ic = Vec::with_capacity(
+        size_of::<IoAPIC>() + (MAX_SUPPORTED_VCPUS as usize) * size_of::<LocalAPIC>(),
+    );
 
     ic.extend_from_slice(IoAPIC::new(0, layout::IOAPIC_ADDR).as_bytes());
-    for i in 0..nr_vcpus {
-        ic.extend_from_slice(LocalAPIC::new(i).as_bytes());
+    for i in 0..MAX_SUPPORTED_VCPUS {
+        if i < nr_vcpus {
+            ic.extend_from_slice(LocalAPIC::new(i, true).as_bytes());
+        } else {
+            ic.extend_from_slice(LocalAPIC::new(i, false).as_bytes())
+        }
     }
     ic
 }