From b6801e355ec58222d60e7af5b60fa76da9d19d66 Mon Sep 17 00:00:00 2001
From: Rob Bradford <robert.bradford@intel.com>
Date: Tue, 26 Nov 2019 13:06:24 +0000
Subject: [PATCH] vmm: cpu: Refactor vCPU thread starting

Refactor the vCPU thread starting so that there is the possibility to
bring on extra vCPU threads.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
---
 vmm/src/cpu.rs | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/vmm/src/cpu.rs b/vmm/src/cpu.rs
index 538ae500c..25ca31c0d 100644
--- a/vmm/src/cpu.rs
+++ b/vmm/src/cpu.rs
@@ -117,6 +117,9 @@ pub enum Error {
 
     /// Failed to allocate IO port
     AllocateIOPort,
+
+    /// Asking for more vCPUs that we can have
+    DesiredVCPUCountExceedsMax,
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -444,7 +447,7 @@ impl CpuManager {
             fd,
             vcpus_kill_signalled: Arc::new(AtomicBool::new(false)),
             vcpus_pause_signalled: Arc::new(AtomicBool::new(false)),
-            threads: Vec::with_capacity(boot_vcpus as usize),
+            vcpu_states: Vec::with_capacity(max_vcpus as usize),
             reset_evt,
             selected_cpu: 0,
         }));
@@ -468,13 +471,17 @@ impl CpuManager {
         Ok(cpu_manager)
     }
 
-    // Starts all the vCPUs that the VM is booting with. Blocks until all vCPUs are running.
-    pub fn start_boot_vcpus(&mut self, entry_addr: GuestAddress) -> Result<()> {
+    fn activate_vcpus(&mut self, desired_vcpus: u8, entry_addr: GuestAddress) -> Result<()> {
+        if desired_vcpus > self.max_vcpus {
+            return Err(Error::DesiredVCPUCountExceedsMax);
+        }
+
         let creation_ts = std::time::Instant::now();
+        let vcpu_thread_barrier = Arc::new(Barrier::new(
+            (desired_vcpus - self.present_vcpus() + 1) as usize,
+        ));
 
-        let vcpu_thread_barrier = Arc::new(Barrier::new((self.boot_vcpus + 1) as usize));
-
-        for cpu_id in 0..self.boot_vcpus {
+        for cpu_id in self.present_vcpus()..desired_vcpus {
             let ioapic = if let Some(ioapic) = &self.ioapic {
                 Some(ioapic.clone())
             } else {
@@ -559,6 +566,11 @@ impl CpuManager {
         Ok(())
     }
 
+    // Starts all the vCPUs that the VM is booting with. Blocks until all vCPUs are running.
+    pub fn start_boot_vcpus(&mut self, entry_addr: GuestAddress) -> Result<()> {
+        self.activate_vcpus(self.boot_vcpus(), entry_addr)
+    }
+
     pub fn shutdown(&mut self) -> Result<()> {
         // Tell the vCPUs to stop themselves next time they go through the loop
         self.vcpus_kill_signalled.store(true, Ordering::SeqCst);