vmm: Add boot and max vCPU handling to command line parser

Also retain support (with a warning for the old behaviour.)

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

src/main.rs

@@ -346,7 +346,7 @@ fn main() {
         "Cloud Hypervisor Guest\n\tAPI server: {}\n\tvCPUs: {}\n\tMemory: {} MB\
          \n\tKernel: {:?}\n\tKernel cmdline: {}\n\tDisk(s): {:?}",
         api_socket_path,
-        vm_config.cpus.cpu_count,
+        vm_config.cpus.boot_vcpus,
         vm_config.memory.size >> 20,
         vm_config.kernel,
         vm_config.cmdline.args.as_str(),
@@ -923,7 +923,8 @@ mod tests {
         }
 
         fn api_create_body(&self, cpu_count: u8) -> String {
-            format! {"{{\"cpus\":{{\"cpu_count\":{}}},\"kernel\":{{\"path\":\"{}\"}},\"cmdline\":{{\"args\": \"\"}},\"net\":[{{\"ip\":\"{}\", \"mask\":\"255.255.255.0\", \"mac\":\"{}\"}}], \"disks\":[{{\"path\":\"{}\"}}, {{\"path\":\"{}\"}}]}}",
+            format! {"{{\"cpus\":{{\"boot_vcpus\":{},\"max_vcpus\":{}}},\"kernel\":{{\"path\":\"{}\"}},\"cmdline\":{{\"args\": \"\"}},\"net\":[{{\"ip\":\"{}\", \"mask\":\"255.255.255.0\", \"mac\":\"{}\"}}], \"disks\":[{{\"path\":\"{}\"}}, {{\"path\":\"{}\"}}]}}",
+                     cpu_count,
                      cpu_count,
                      self.fw_path.as_str(),
                      self.network.host_ip,

vmm/src/config.rs

@@ -21,6 +21,10 @@ pub const DEFAULT_RNG_SOURCE: &str = "/dev/urandom";
 pub enum Error<'a> {
     /// Failed parsing cpus parameters.
     ParseCpusParams(std::num::ParseIntError),
+    /// Unexpected vCPU parameter
+    ParseCpusUnknownParam,
+    /// Max is less than boot
+    ParseCpusMaxLowerThanBoot,
     /// Failed parsing memory file parameter.
     ParseMemoryFileParam,
     /// Failed parsing kernel parameters.
@@ -132,21 +136,59 @@ fn parse_on_off(param: &str) -> Result<bool> {
 
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub struct CpusConfig {
-    pub cpu_count: u8,
+    pub boot_vcpus: u8,
+    pub max_vcpus: u8,
 }
 
 impl CpusConfig {
     pub fn parse(cpus: &str) -> Result<Self> {
-        Ok(CpusConfig {
-            cpu_count: cpus.parse().map_err(Error::ParseCpusParams)?,
-        })
+        if let Ok(legacy_vcpu_count) = cpus.parse::<u8>() {
+            error!("Using deprecated vCPU syntax. Use --cpus boot=<boot_vcpus>[,max=<max_vcpus]");
+            Ok(CpusConfig {
+                boot_vcpus: legacy_vcpu_count,
+                max_vcpus: legacy_vcpu_count,
+            })
+        } else {
+            // Split the parameters based on the comma delimiter
+            let params_list: Vec<&str> = cpus.split(',').collect();
+
+            let mut boot_str: &str = "";
+            let mut max_str: &str = "";
+
+            for param in params_list.iter() {
+                if param.starts_with("boot=") {
+                    boot_str = &param["boot=".len()..];
+                } else if param.starts_with("max=") {
+                    max_str = &param["max=".len()..];
+                } else {
+                    return Err(Error::ParseCpusUnknownParam);
+                }
+            }
+
+            let boot_vcpus: u8 = boot_str.parse().map_err(Error::ParseCpusParams)?;
+            let max_vcpus = if max_str != "" {
+                max_str.parse().map_err(Error::ParseCpusParams)?
+            } else {
+                boot_vcpus
+            };
+
+            if max_vcpus < boot_vcpus {
+                return Err(Error::ParseCpusMaxLowerThanBoot);
+            }
+
+            Ok(CpusConfig {
+                boot_vcpus,
+                max_vcpus,
+            })
+        }
     }
 }
 
 impl Default for CpusConfig {
     fn default() -> Self {
         CpusConfig {
-            cpu_count: DEFAULT_VCPUS,
+            boot_vcpus: DEFAULT_VCPUS,
+            max_vcpus: DEFAULT_VCPUS,
         }
     }
 }

vmm/src/vm.rs

@@ -450,8 +450,8 @@ impl Vm {
 
         let on_tty = unsafe { libc::isatty(libc::STDIN_FILENO as i32) } != 0;
 
-        let boot_vcpus = config.cpus.cpu_count;
-        let max_vcpus = config.cpus.cpu_count;
+        let boot_vcpus = config.cpus.boot_vcpus;
+        let max_vcpus = config.cpus.max_vcpus;
         let cpu_manager = cpu::CpuManager::new(
             boot_vcpus,
             max_vcpus,