hypervisor, vmm: Feature guard KVM specific code

There are some code base and function which are purely KVM specific for
now and we don't have those supports in mshv at the moment but we have plan
for the future. We are doing a feature guard with KVM. For example, KVM has
mp_state, cpu clock support,  which we don't have for mshv. In order to build
those code we are making the code base for KVM specific compilation.

Signed-off-by: Muminul Islam <muislam@microsoft.com>

hypervisor/src/cpu.rs

@@ -272,10 +272,12 @@ pub trait Vcpu: Send + Sync {
     /// Setup the model-specific registers (MSR) for this vCPU.
     ///
     fn set_msrs(&self, msrs: &MsrEntries) -> Result<usize>;
+    #[cfg(feature = "kvm")]
     ///
     /// Returns the vcpu's current "multiprocessing state".
     ///
     fn get_mp_state(&self) -> Result<MpState>;
+    #[cfg(feature = "kvm")]
     ///
     /// Sets the vcpu's current "multiprocessing state".
     ///
@@ -312,7 +314,7 @@ pub trait Vcpu: Send + Sync {
     /// of the vcpu.
     ///
     fn set_vcpu_events(&self, events: &VcpuEvents) -> Result<()>;
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(all(feature = "kvm", target_arch = "x86_64"))]
     ///
     /// Let the guest know that it has been paused, which prevents from
     /// potential soft lockups when being resumed.

hypervisor/src/hypervisor.rs

@@ -10,7 +10,7 @@
 use crate::vm::Vm;
 #[cfg(target_arch = "x86_64")]
 use crate::x86_64::{CpuId, MsrList};
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(feature = "kvm", target_arch = "x86_64"))]
 use kvm_ioctls::Cap;
 use std::sync::Arc;
 
@@ -78,19 +78,22 @@ pub trait Hypervisor: Send + Sync {
     /// Return a hypervisor-agnostic Vm trait object
     ///
     fn create_vm(&self) -> Result<Arc<dyn Vm>>;
+    #[cfg(feature = "kvm")]
     ///
     /// Returns the size of the memory mapping required to use the vcpu's structures
     ///
     fn get_vcpu_mmap_size(&self) -> Result<usize>;
+    #[cfg(feature = "kvm")]
     ///
     /// Gets the recommended maximum number of VCPUs per VM.
     ///
     fn get_max_vcpus(&self) -> Result<usize>;
+    #[cfg(feature = "kvm")]
     ///
     /// Gets the recommended number of VCPUs per VM.
     ///
     fn get_nr_vcpus(&self) -> Result<usize>;
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(all(feature = "kvm", target_arch = "x86_64"))]
     ///
     /// Checks if a particular `Cap` is available.
     ///

hypervisor/src/lib.rs

@@ -28,6 +28,7 @@ extern crate serde_derive;
 extern crate serde_json;
 extern crate thiserror;
 
+#[cfg(feature = "kvm")]
 /// KVM implementation module
 pub mod kvm;
 
@@ -49,6 +50,7 @@ mod device;
 pub use crate::hypervisor::{Hypervisor, HypervisorError};
 pub use cpu::{HypervisorCpuError, Vcpu, VmExit};
 pub use device::{Device, HypervisorDeviceError};
+#[cfg(feature = "kvm")]
 pub use kvm::*;
 pub use vm::{DataMatch, HypervisorVmError, Vm};
 

hypervisor/src/vm.rs

@@ -12,10 +12,12 @@
 use crate::aarch64::VcpuInit;
 use crate::cpu::Vcpu;
 use crate::device::Device;
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(feature = "kvm", target_arch = "x86_64"))]
 use crate::ClockData;
+#[cfg(feature = "kvm")]
 use crate::KvmVmState as VmState;
 use crate::{CreateDevice, IoEventAddress, IrqRoutingEntry, MemoryRegion};
+#[cfg(feature = "kvm")]
 use kvm_ioctls::Cap;
 use std::sync::Arc;
 use thiserror::Error;
@@ -198,6 +200,7 @@ pub trait Vm: Send + Sync {
     ) -> MemoryRegion;
     /// Creates/modifies a guest physical memory slot.
     fn set_user_memory_region(&self, user_memory_region: MemoryRegion) -> Result<()>;
+    #[cfg(feature = "kvm")]
     /// Creates an emulated device in the kernel.
     fn create_device(&self, device: &mut CreateDevice) -> Result<Arc<dyn Device>>;
     /// Returns the preferred CPU target type which can be emulated by KVM on underlying host.
@@ -207,11 +210,12 @@ pub trait Vm: Send + Sync {
     #[cfg(target_arch = "x86_64")]
     fn enable_split_irq(&self) -> Result<()>;
     /// Retrieve guest clock.
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(all(feature = "kvm", target_arch = "x86_64"))]
     fn get_clock(&self) -> Result<ClockData>;
     /// Set guest clock.
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(all(feature = "kvm", target_arch = "x86_64"))]
     fn set_clock(&self, data: &ClockData) -> Result<()>;
+    #[cfg(feature = "kvm")]
     /// Checks if a particular `Cap` is available.
     fn check_extension(&self, c: Cap) -> bool;
     /// Create a device that is used for passthrough