add mem_config parameter to machine-config endpoint (aarch64)

Add a mem_config parameter to the PUT/PATCH /machine-config endpoints,
which allows configuration of the size of a swiotlb region to use.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/firecracker/src/api_server/request/machine_configuration.rs

@@ -119,6 +119,7 @@ mod tests {
             let expected_config = MachineConfigUpdate {
                 vcpu_count: Some(8),
                 mem_size_mib: Some(1024),
+                mem_config: Some(Default::default()),
                 smt: Some(false),
                 cpu_template: None,
                 track_dirty_pages: Some(false),
@@ -140,6 +141,7 @@ mod tests {
         let expected_config = MachineConfigUpdate {
             vcpu_count: Some(8),
             mem_size_mib: Some(1024),
+            mem_config: Some(Default::default()),
             smt: Some(false),
             cpu_template: Some(StaticCpuTemplate::None),
             track_dirty_pages: Some(false),
@@ -161,6 +163,7 @@ mod tests {
         let expected_config = MachineConfigUpdate {
             vcpu_count: Some(8),
             mem_size_mib: Some(1024),
+            mem_config: Some(Default::default()),
             smt: Some(false),
             cpu_template: None,
             track_dirty_pages: Some(true),
@@ -186,6 +189,7 @@ mod tests {
             let expected_config = MachineConfigUpdate {
                 vcpu_count: Some(8),
                 mem_size_mib: Some(1024),
+                mem_config: Some(Default::default()),
                 smt: Some(false),
                 cpu_template: Some(StaticCpuTemplate::T2),
                 track_dirty_pages: Some(true),
@@ -213,6 +217,7 @@ mod tests {
         let expected_config = MachineConfigUpdate {
             vcpu_count: Some(8),
             mem_size_mib: Some(1024),
+            mem_config: Some(Default::default()),
             smt: Some(true),
             cpu_template: None,
             track_dirty_pages: Some(true),

src/vmm/src/persist.rs

@@ -33,7 +33,9 @@ use crate::snapshot::Snapshot;
 use crate::utils::u64_to_usize;
 use crate::vmm_config::boot_source::BootSourceConfig;
 use crate::vmm_config::instance_info::InstanceInfo;
-use crate::vmm_config::machine_config::{HugePageConfig, MachineConfigError, MachineConfigUpdate};
+use crate::vmm_config::machine_config::{
+    HugePageConfig, MachineConfigError, MachineConfigUpdate, MemoryConfig,
+};
 use crate::vmm_config::snapshot::{CreateSnapshotParams, LoadSnapshotParams, MemBackendType};
 use crate::vstate::kvm::KvmState;
 use crate::vstate::memory;
@@ -47,6 +49,8 @@ use crate::{EventManager, Vmm, vstate};
 pub struct VmInfo {
     /// Guest memory size.
     pub mem_size_mib: u64,
+    /// Memory config
+    pub mem_config: MemoryConfig,
     /// smt information
     pub smt: bool,
     /// CPU template type
@@ -61,6 +65,7 @@ impl From<&VmResources> for VmInfo {
     fn from(value: &VmResources) -> Self {
         Self {
             mem_size_mib: value.machine_config.mem_size_mib as u64,
+            mem_config: value.machine_config.mem_config,
             smt: value.machine_config.smt,
             cpu_template: StaticCpuTemplate::from(&value.machine_config.cpu_template),
             boot_source: value.boot_source.config.clone(),
@@ -360,6 +365,7 @@ pub fn restore_from_snapshot(
         .update_machine_config(&MachineConfigUpdate {
             vcpu_count: Some(vcpu_count),
             mem_size_mib: Some(u64_to_usize(microvm_state.vm_info.mem_size_mib)),
+            mem_config: Some(microvm_state.vm_info.mem_config),
             smt: Some(microvm_state.vm_info.smt),
             cpu_template: Some(microvm_state.vm_info.cpu_template),
             track_dirty_pages: Some(track_dirty_pages),

src/vmm/src/resources.rs

@@ -1302,6 +1302,7 @@ mod tests {
         let mut aux_vm_config = MachineConfigUpdate {
             vcpu_count: Some(32),
             mem_size_mib: Some(512),
+            mem_config: Some(Default::default()),
             smt: Some(false),
             #[cfg(target_arch = "x86_64")]
             cpu_template: Some(StaticCpuTemplate::T2),

src/vmm/src/vmm_config/machine_config.rs

@@ -20,6 +20,9 @@ pub enum MachineConfigError {
     IncompatibleBalloonSize,
     /// The memory size (MiB) is either 0, or not a multiple of the configured page size.
     InvalidMemorySize,
+    /// The specified swiotlb region matches or exceeds the total VM memory, or not a multiple of the configured page size.
+    #[cfg(target_arch = "aarch64")]
+    InvalidSwiotlbRegionSize,
     /// The number of vCPUs must be greater than 0, less than {MAX_SUPPORTED_VCPUS:} and must be 1 or an even number if SMT is enabled.
     InvalidVcpuCount,
     /// Could not get the configuration of the previously installed balloon device to validate the memory size.
@@ -89,6 +92,17 @@ impl From<HugePageConfig> for Option<memfd::HugetlbSize> {
     }
 }
 
+/// Structure containing options for tweaking guest memory configuration.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Deserialize, Serialize)]
+pub struct MemoryConfig {
+    /// The initial size of the swiotlb region. If 0, no swiotlb region will be created.
+    /// If non-zero, all device will be forced to bounce buffers through a swiotlb region
+    /// of the specified size that will have been placed into a dedicated kvm memslot.
+    #[cfg(target_arch = "aarch64")]
+    #[serde(default)]
+    pub initial_swiotlb_size: usize,
+}
+
 /// Struct used in PUT `/machine-config` API call.
 #[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize)]
 #[serde(deny_unknown_fields)]
@@ -97,6 +111,10 @@ pub struct MachineConfig {
     pub vcpu_count: u8,
     /// The memory size in MiB.
     pub mem_size_mib: usize,
+    /// Additional configuration options for guest memory
+    #[serde(default)]
+    #[serde(skip_serializing_if = "is_default")]
+    pub mem_config: MemoryConfig,
     /// Enables or disabled SMT.
     #[serde(default)]
     pub smt: bool,
@@ -121,6 +139,10 @@ pub struct MachineConfig {
     pub gdb_socket_path: Option<String>,
 }
 
+fn is_default<T: Default + Eq>(t: &T) -> bool {
+    t == &T::default()
+}
+
 fn is_none_or_custom_template(template: &Option<CpuTemplateType>) -> bool {
     matches!(template, None | Some(CpuTemplateType::Custom(_)))
 }
@@ -153,6 +175,7 @@ impl Default for MachineConfig {
         Self {
             vcpu_count: 1,
             mem_size_mib: DEFAULT_MEM_SIZE_MIB,
+            mem_config: Default::default(),
             smt: false,
             cpu_template: None,
             track_dirty_pages: false,
@@ -178,6 +201,9 @@ pub struct MachineConfigUpdate {
     /// The memory size in MiB.
     #[serde(default)]
     pub mem_size_mib: Option<usize>,
+    /// The memory configuration
+    #[serde(default)]
+    pub mem_config: Option<MemoryConfig>,
     /// Enables or disabled SMT.
     #[serde(default)]
     pub smt: Option<bool>,
@@ -210,6 +236,7 @@ impl From<MachineConfig> for MachineConfigUpdate {
         MachineConfigUpdate {
             vcpu_count: Some(cfg.vcpu_count),
             mem_size_mib: Some(cfg.mem_size_mib),
+            mem_config: Some(cfg.mem_config),
             smt: Some(cfg.smt),
             cpu_template: cfg.static_template(),
             track_dirty_pages: Some(cfg.track_dirty_pages),
@@ -263,11 +290,19 @@ impl MachineConfig {
 
         let mem_size_mib = update.mem_size_mib.unwrap_or(self.mem_size_mib);
         let page_config = update.huge_pages.unwrap_or(self.huge_pages);
+        let mem_config = update.mem_config.unwrap_or(self.mem_config);
 
         if mem_size_mib == 0 || !page_config.is_valid_mem_size(mem_size_mib) {
             return Err(MachineConfigError::InvalidMemorySize);
         }
 
+        #[cfg(target_arch = "aarch64")]
+        if mem_config.initial_swiotlb_size >= mem_size_mib
+            || !page_config.is_valid_mem_size(mem_config.initial_swiotlb_size)
+        {
+            return Err(MachineConfigError::InvalidSwiotlbRegionSize);
+        }
+
         let cpu_template = match update.cpu_template {
             None => self.cpu_template.clone(),
             Some(StaticCpuTemplate::None) => None,
@@ -277,6 +312,7 @@ impl MachineConfig {
         Ok(MachineConfig {
             vcpu_count,
             mem_size_mib,
+            mem_config,
             smt,
             cpu_template,
             track_dirty_pages: update.track_dirty_pages.unwrap_or(self.track_dirty_pages),