misc: Change cpu ID type from u8 to u32

This is the first change to Cloud Hypervisor in a series of changes
intended to increase the max number of supported vCPUs in guest VMs,
which is currently limited to 255 (254 on x86_64).

No user-visible/behavior changes are expected as a result of
applying this patch, as the type of boot_cpus and related
fields in config structs remains u8 for now, and all configuration
validations remain the same.

Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Neel Natu <neelnatu@google.com>
Signed-off-by: Ofir Weisse <oweisse@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>

arch/src/aarch64/fdt.rs

@@ -370,7 +370,7 @@ fn create_cpu_nodes(
         if numa_nodes.len() > 1 {
             for numa_node_idx in 0..numa_nodes.len() {
                 let numa_node = numa_nodes.get(&(numa_node_idx as u32));
-                if numa_node.unwrap().cpus.contains(&(cpu_id as u8)) {
+                if numa_node.unwrap().cpus.contains(&(cpu_id as u32)) {
                     fdt.property_u32("numa-node-id", numa_node_idx as u32)?;
                 }
             }

arch/src/aarch64/mod.rs

@@ -67,7 +67,7 @@ pub struct EntryPoint {
 /// Configure the specified VCPU, and return its MPIDR.
 pub fn configure_vcpu(
     vcpu: &Arc<dyn hypervisor::Vcpu>,
-    id: u8,
+    id: u32,
     boot_setup: Option<(EntryPoint, &GuestMemoryAtomic<GuestMemoryMmap>)>,
 ) -> super::Result<u64> {
     if let Some((kernel_entry_point, _guest_memory)) = boot_setup {

arch/src/lib.rs

@@ -123,7 +123,7 @@ fn pagesize() -> usize {
 pub struct NumaNode {
     pub memory_regions: Vec<Arc<GuestRegionMmap>>,
     pub hotplug_regions: Vec<Arc<GuestRegionMmap>>,
-    pub cpus: Vec<u8>,
+    pub cpus: Vec<u32>,
     pub pci_segments: Vec<u16>,
     pub distances: BTreeMap<u32, u8>,
     pub memory_zones: Vec<String>,

arch/src/riscv64/mod.rs

@@ -59,7 +59,7 @@ pub struct EntryPoint {
 /// Configure the specified VCPU, and return its MPIDR.
 pub fn configure_vcpu(
     vcpu: &Arc<dyn hypervisor::Vcpu>,
-    id: u8,
+    id: u32,
     boot_setup: Option<(EntryPoint, &GuestMemoryAtomic<GuestMemoryMmap>)>,
 ) -> super::Result<()> {
     if let Some((kernel_entry_point, _guest_memory)) = boot_setup {

arch/src/x86_64/mod.rs

@@ -820,14 +820,14 @@ pub fn generate_common_cpuid(
 
 pub fn configure_vcpu(
     vcpu: &Arc<dyn hypervisor::Vcpu>,
-    id: u8,
+    id: u32,
     boot_setup: Option<(EntryPoint, &GuestMemoryAtomic<GuestMemoryMmap>)>,
     cpuid: Vec<CpuIdEntry>,
     kvm_hyperv: bool,
     cpu_vendor: CpuVendor,
     topology: Option<(u8, u8, u8)>,
 ) -> super::Result<()> {
-    let x2apic_id = get_x2apic_id(id as u32, topology);
+    let x2apic_id = get_x2apic_id(id, topology);
 
     // Per vCPU CPUID changes; common are handled via generate_common_cpuid()
     let mut cpuid = cpuid;
@@ -946,7 +946,7 @@ pub fn configure_system(
     cmdline_addr: GuestAddress,
     cmdline_size: usize,
     initramfs: &Option<InitramfsConfig>,
-    _num_cpus: u8,
+    _num_cpus: u32,
     setup_header: Option<setup_header>,
     rsdp_addr: Option<GuestAddress>,
     sgx_epc_region: Option<SgxEpcRegion>,
@@ -1365,10 +1365,10 @@ fn update_cpuid_topology(
     cores_per_die: u8,
     dies_per_package: u8,
     cpu_vendor: CpuVendor,
-    id: u8,
+    id: u32,
 ) {
     let x2apic_id = get_x2apic_id(
-        id as u32,
+        id,
         Some((threads_per_core, cores_per_die, dies_per_package)),
     );
 

arch/src/x86_64/mptable.rs

@@ -121,7 +121,7 @@ fn mpf_intel_compute_checksum(v: &mpspec::mpf_intel) -> u8 {
     (!checksum).wrapping_add(1)
 }
 
-fn compute_mp_size(num_cpus: u8) -> usize {
+fn compute_mp_size(num_cpus: u32) -> usize {
     mem::size_of::<MpfIntelWrapper>()
         + mem::size_of::<MpcTableWrapper>()
         + mem::size_of::<MpcCpuWrapper>() * (num_cpus as usize)
@@ -135,12 +135,12 @@ fn compute_mp_size(num_cpus: u8) -> usize {
 pub fn setup_mptable(
     offset: GuestAddress,
     mem: &GuestMemoryMmap,
-    num_cpus: u8,
+    num_cpus: u32,
     topology: Option<(u8, u8, u8)>,
 ) -> Result<()> {
     if num_cpus > 0 {
         let cpu_id_max = num_cpus - 1;
-        let x2apic_id_max = get_x2apic_id(cpu_id_max.into(), topology);
+        let x2apic_id_max = get_x2apic_id(cpu_id_max, topology);
         if x2apic_id_max >= MAX_SUPPORTED_CPUS {
             return Err(Error::TooManyCpus);
         }
@@ -195,7 +195,7 @@ pub fn setup_mptable(
         for cpu_id in 0..num_cpus {
             let mut mpc_cpu = MpcCpuWrapper(mpspec::mpc_cpu::default());
             mpc_cpu.0.type_ = mpspec::MP_PROCESSOR as u8;
-            mpc_cpu.0.apicid = get_x2apic_id(cpu_id as u32, topology) as u8;
+            mpc_cpu.0.apicid = get_x2apic_id(cpu_id, topology) as u8;
             mpc_cpu.0.apicver = APIC_VERSION;
             mpc_cpu.0.cpuflag = mpspec::CPU_ENABLED as u8
                 | if cpu_id == 0 {
@@ -392,13 +392,11 @@ mod tests {
 
     #[test]
     fn cpu_entry_count() {
-        let mem = GuestMemoryMmap::from_ranges(&[(
-            MPTABLE_START,
-            compute_mp_size(MAX_SUPPORTED_CPUS as u8),
-        )])
-        .unwrap();
+        let mem =
+            GuestMemoryMmap::from_ranges(&[(MPTABLE_START, compute_mp_size(MAX_SUPPORTED_CPUS))])
+                .unwrap();
 
-        for i in 0..MAX_SUPPORTED_CPUS as u8 {
+        for i in 0..MAX_SUPPORTED_CPUS {
             setup_mptable(MPTABLE_START, &mem, i, None).unwrap();
 
             let mpf_intel: MpfIntelWrapper = mem.read_obj(MPTABLE_START).unwrap();
@@ -429,10 +427,9 @@ mod tests {
     #[test]
     fn cpu_entry_count_max() {
         let cpus = MAX_SUPPORTED_CPUS + 1;
-        let mem =
-            GuestMemoryMmap::from_ranges(&[(MPTABLE_START, compute_mp_size(cpus as u8))]).unwrap();
+        let mem = GuestMemoryMmap::from_ranges(&[(MPTABLE_START, compute_mp_size(cpus))]).unwrap();
 
-        let result = setup_mptable(MPTABLE_START, &mem, cpus as u8, None);
+        let result = setup_mptable(MPTABLE_START, &mem, cpus, None);
         result.unwrap_err();
     }
 }