hypervisor: support AArch64 get_host_ipa_limit

Not all AArch64 platforms support IPAs up to 40 bits. Since the
kvm-ioctl crate now supports `get_host_ipa_limit` for AArch64,
when creating the VM, it is better to get the IPA size from the
host and use that to create the VM.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

Author: MrXinWang

hypervisor/src/kvm/mod.rs

@@ -22,6 +22,8 @@ use crate::vm::{self, VmmOps};
 use crate::{arm64_core_reg_id, offset__of};
 use kvm_ioctls::{NoDatamatch, VcpuFd, VmFd};
 use serde_derive::{Deserialize, Serialize};
+#[cfg(target_arch = "aarch64")]
+use std::convert::TryInto;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::result;
 #[cfg(target_arch = "x86_64")]
@@ -558,7 +560,18 @@ impl hypervisor::Hypervisor for KvmHypervisor {
     /// let vm = hypervisor.create_vm().unwrap()
     ///
     fn create_vm(&self) -> hypervisor::Result<Arc<dyn vm::Vm>> {
-        self.create_vm_with_type(0) // Create with default platform type
+        #[allow(unused_mut)]
+        let mut vm_type: u64 = 0; // Create with default platform type
+
+        // When KVM supports Cap::ArmVmIPASize, it is better to get the IPA
+        // size from the host and use that when creating the VM, which may
+        // avoid unnecessary VM creation failures.
+        #[cfg(target_arch = "aarch64")]
+        if self.kvm.check_extension(Cap::ArmVmIPASize) {
+            vm_type = self.kvm.get_host_ipa_limit().try_into().unwrap();
+        }
+
+        self.create_vm_with_type(vm_type)
     }
 
     fn check_required_extensions(&self) -> hypervisor::Result<()> {
@@ -575,6 +588,7 @@ impl hypervisor::Hypervisor for KvmHypervisor {
             .get_supported_cpuid(kvm_bindings::KVM_MAX_CPUID_ENTRIES)
             .map_err(|e| hypervisor::HypervisorError::GetCpuId(e.into()))
     }
+
     #[cfg(target_arch = "x86_64")]
     ///
     /// Retrieve the list of MSRs supported by KVM.