hypervisor: hypervisor_type method on Vcpu trait

Although it is already possible to obtain the hypervisor type from the
hypervisor trait object, there is currently no way for functions that
only have a vCPU object to work with to know what the hypervisor
backend is.

In the rare case where there is significant divergence between the
supported hypervisor backends when working with vCPU objects the caller
must necessarily branch on the hypervisor type.

We thus introduce a hypervisor_type method on the Vcpu trait.

This will be utilized in a follow up commit where we need special
handling when configuring MSRs of vCPUs.

Signed-off-by: Oliver Anderson <oliver.anderson@cyberus-technology.de>
On-behalf-of: SAP oliver.anderson@sap.com

hypervisor/src/cpu.rs

@@ -30,7 +30,7 @@ use crate::arch::aarch64::ExtendedReg;
 use crate::arch::x86::{CpuIdEntry, FpuState, LapicState, MsrEntry, SpecialRegisters};
 #[cfg(feature = "tdx")]
 use crate::kvm::{TdxExitDetails, TdxExitStatus};
-use crate::{CpuState, MpState, StandardRegisters};
+use crate::{CpuState, HypervisorType, MpState, StandardRegisters};
 
 #[cfg(target_arch = "x86_64")]
 #[derive(Copy, Clone, Debug, Default, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
@@ -679,4 +679,9 @@ pub trait Vcpu: Send + Sync {
     /// Trigger NMI interrupt
     ///
     fn nmi(&self) -> Result<()>;
+
+    ///
+    /// The type of the hypervisor backing this vCPU
+    ///
+    fn hypervisor_type(&self) -> HypervisorType;
 }

hypervisor/src/kvm/mod.rs

@@ -3765,6 +3765,10 @@ impl cpu::Vcpu for KvmVcpu {
 
         Ok(())
     }
+
+    fn hypervisor_type(&self) -> HypervisorType {
+        HypervisorType::Kvm
+    }
 }
 
 #[cfg(target_arch = "aarch64")]

hypervisor/src/mshv/mod.rs

@@ -1626,6 +1626,10 @@ impl cpu::Vcpu for MshvVcpu {
 
         Ok(())
     }
+
+    fn hypervisor_type(&self) -> HypervisorType {
+        HypervisorType::Mshv
+    }
 }
 
 impl MshvVcpu {