Add seccomp filters to VMM

Add seccompiler filters as a field of the VMM. This is required to
ensure that the newly created vCPU threads have the same filters as the
currently existing vCPU threads

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

Author: JamesC1305

src/vmm/src/builder.rs

@@ -139,13 +139,15 @@ impl std::convert::From<linux_loader::cmdline::Error> for StartMicrovmError {
 }
 
 #[cfg_attr(target_arch = "aarch64", allow(unused))]
+#[allow(clippy::too_many_arguments)]
 fn create_vmm_and_vcpus(
     instance_info: &InstanceInfo,
     event_manager: &mut EventManager,
     guest_memory: GuestMemoryMmap,
     uffd: Option<Uffd>,
     track_dirty_pages: bool,
     vcpu_count: u8,
+    #[cfg(target_arch = "x86_64")] seccomp_filters: BpfThreadMap,
     kvm_capabilities: Vec<KvmCapability>,
 ) -> Result<(Vmm, Vec<Vcpu>), StartMicrovmError> {
     use self::StartMicrovmError::*;
@@ -222,6 +224,8 @@ fn create_vmm_and_vcpus(
         uffd,
         vcpus_handles: Vec::new(),
         vcpus_exit_evt,
+        #[cfg(target_arch = "x86_64")]
+        seccomp_filters,
         resource_allocator,
         mmio_device_manager,
         #[cfg(target_arch = "x86_64")]
@@ -301,6 +305,8 @@ pub fn build_microvm_for_boot(
         None,
         track_dirty_pages,
         vm_resources.vm_config.vcpu_count,
+        #[cfg(target_arch = "x86_64")]
+        seccomp_filters.clone(),
         cpu_template.kvm_capabilities.clone(),
     )?;
 
@@ -468,6 +474,8 @@ pub fn build_microvm_from_snapshot(
         uffd,
         vm_resources.vm_config.track_dirty_pages,
         vm_resources.vm_config.vcpu_count,
+        #[cfg(target_arch = "x86_64")]
+        seccomp_filters.clone(),
         microvm_state.vm_state.kvm_cap_modifiers.clone(),
     )?;
 
@@ -1142,6 +1150,8 @@ pub mod tests {
             uffd: None,
             vcpus_handles: Vec::new(),
             vcpus_exit_evt,
+            #[cfg(target_arch = "x86_64")]
+            seccomp_filters: crate::seccomp_filters::get_empty_filters(),
             resource_allocator: ResourceAllocator::new().unwrap(),
             mmio_device_manager,
             #[cfg(target_arch = "x86_64")]

src/vmm/src/lib.rs

@@ -122,11 +122,17 @@ use device_manager::resources::ResourceAllocator;
 use devices::acpi::vmgenid::VmGenIdError;
 use event_manager::{EventManager as BaseEventManager, EventOps, Events, MutEventSubscriber};
 use seccompiler::BpfProgram;
+#[cfg(target_arch = "x86_64")]
+use seccompiler::BpfThreadMap;
 use userfaultfd::Uffd;
 use utils::epoll::EventSet;
 use utils::eventfd::EventFd;
 use utils::terminal::Terminal;
 use utils::u64_to_usize;
+#[cfg(target_arch = "x86_64")]
+use vmm_config::hotplug::{HotplugVcpuConfig, HotplugVcpuError};
+#[cfg(target_arch = "x86_64")]
+use vmm_config::machine_config::{MachineConfigUpdate, MAX_SUPPORTED_VCPUS};
 use vstate::vcpu::{self, KvmVcpuConfigureError, StartThreadedError, VcpuSendEventError};
 
 use crate::arch::DeviceType;
@@ -314,6 +320,9 @@ pub struct Vmm {
     vcpus_handles: Vec<VcpuHandle>,
     // Used by Vcpus and devices to initiate teardown; Vmm should never write here.
     vcpus_exit_evt: EventFd,
+    // seccomp_filters are only needed in VMM for hotplugging vCPUS.
+    #[cfg(target_arch = "x86_64")]
+    seccomp_filters: BpfThreadMap,
 
     // Allocator for guest resources
     resource_allocator: ResourceAllocator,
@@ -594,6 +603,66 @@ impl Vmm {
         Ok(cpu_configs)
     }
 
+    /// Adds new vCPUs to VMM.
+    #[cfg(target_arch = "x86_64")]
+    pub fn hotplug_vcpus(
+        &mut self,
+        config: HotplugVcpuConfig,
+    ) -> Result<MachineConfigUpdate, HotplugVcpuError> {
+        use crate::logger::IncMetric;
+        if config.vcpu_count < 1 {
+            return Err(HotplugVcpuError::VcpuCountTooLow);
+        } else if self
+            .vcpus_handles
+            .len()
+            .checked_add(config.vcpu_count.into())
+            .ok_or(HotplugVcpuError::VcpuCountTooHigh)?
+            > MAX_SUPPORTED_VCPUS.into()
+        {
+            return Err(HotplugVcpuError::VcpuCountTooHigh);
+        }
+
+        // Create and start new vcpus
+        let mut vcpus = Vec::with_capacity(config.vcpu_count.into());
+
+        #[allow(clippy::cast_possible_truncation)]
+        let start_idx = self.vcpus_handles.len().try_into().unwrap();
+        for cpu_idx in start_idx..(start_idx + config.vcpu_count) {
+            let exit_evt = self
+                .vcpus_exit_evt
+                .try_clone()
+                .map_err(HotplugVcpuError::EventFd)?;
+            let vcpu =
+                Vcpu::new(cpu_idx, &self.vm, exit_evt).map_err(HotplugVcpuError::VcpuCreate)?;
+            vcpus.push(vcpu);
+        }
+
+        self.start_vcpus(
+            vcpus,
+            self.seccomp_filters
+                .get("vcpu")
+                .ok_or_else(|| HotplugVcpuError::MissingSeccompFilters("vcpu".to_string()))?
+                .clone(),
+        )
+        .map_err(HotplugVcpuError::VcpuStart)?;
+
+        #[allow(clippy::cast_lossless)]
+        METRICS.hotplug.vcpus_added.add(config.vcpu_count.into());
+
+        // Update VM config to reflect new CPUs added
+        #[allow(clippy::cast_possible_truncation)]
+        let new_machine_config = MachineConfigUpdate {
+            vcpu_count: Some(self.vcpus_handles.len() as u8),
+            mem_size_mib: None,
+            smt: None,
+            cpu_template: None,
+            track_dirty_pages: None,
+            huge_pages: None,
+        };
+
+        Ok(new_machine_config)
+    }
+
     /// Retrieves the KVM dirty bitmap for each of the guest's memory regions.
     pub fn reset_dirty_bitmap(&self) {
         self.guest_memory