hypervisor: Add "HyperV" exit to list of KVM exits

Currently we don't need to do anything to service these exits but when
the synthetic interrupt controller is active an exit will be triggered
to notify the VMM of details of the synthetic interrupt page.

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

hypervisor/src/cpu.rs

@@ -167,6 +167,7 @@ pub enum VmExit<'a> {
     MmioWrite(u64 /* address */, &'a [u8]),
     Ignore,
     Reset,
+    Hyperv,
 }
 
 ///

hypervisor/src/kvm/mod.rs

@@ -692,6 +692,7 @@ impl cpu::Vcpu for KvmVcpu {
 
                 VcpuExit::MmioRead(addr, data) => Ok(cpu::VmExit::MmioRead(addr, data)),
                 VcpuExit::MmioWrite(addr, data) => Ok(cpu::VmExit::MmioWrite(addr, data)),
+                VcpuExit::Hyperv => Ok(cpu::VmExit::Hyperv),
 
                 r => Err(cpu::HypervisorCpuError::RunVcpu(anyhow!(
                     "Unexpected exit reason on vcpu run: {:?}",

vmm/src/cpu.rs

@@ -377,6 +377,8 @@ impl Vcpu {
 
                 VmExit::Ignore => Ok(true),
                 VmExit::Reset => Ok(false),
+                // No need to handle anything from a KVM HyperV exit
+                VmExit::Hyperv => Ok(true),
             },
 
             Err(e) => Err(Error::VcpuRun(e.into())),