Add support to get Host_IPA_Limit for AArch64

Host_IPA_Limit is the maximum possible value for
IPA_Bits on the host and is dependent on the CPU capability
and the kernel configuration. The limit can be retrieved using
KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION ioctl.

This commit adds support for getting Host_IPA_Limit for AArch64.

Signed-off-by: Henry Wang <[email protected]>

Author: MrXinWang

coverage_config_aarch64.json

@@ -1,5 +1,5 @@
 {
-  "coverage_score": 76.2,
+  "coverage_score": 76.9,
   "exclude_path": "",
   "crate_features": ""
 }

src/cap.rs

@@ -140,4 +140,5 @@ pub enum Cap {
     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     SplitIrqchip = KVM_CAP_SPLIT_IRQCHIP,
     ImmediateExit = KVM_CAP_IMMEDIATE_EXIT,
+    ArmVmIPASize = KVM_CAP_ARM_VM_IPA_SIZE,
 }

src/ioctls/system.rs

@@ -108,6 +108,14 @@ impl Kvm {
         unsafe { ioctl(self, KVM_GET_API_VERSION()) }
     }
 
+    /// AArch64 specific call to get the host Intermediate Physical Address space limit.
+    ///
+    /// Returns 0 if the capability is not available and an integer larger than 32 otherwise.
+    #[cfg(any(target_arch = "aarch64"))]
+    pub fn get_host_ipa_limit(&self) -> i32 {
+        self.check_extension_int(Cap::ArmVmIPASize)
+    }
+
     /// Wrapper over `KVM_CHECK_EXTENSION`.
     ///
     /// Returns 0 if the capability is not available and a positive integer otherwise.
@@ -412,6 +420,20 @@ mod tests {
         assert!(kvm.check_extension(Cap::UserMemory));
     }
 
+    #[test]
+    #[cfg(any(target_arch = "aarch64"))]
+    fn test_get_host_ipa_limit() {
+        let kvm = Kvm::new().unwrap();
+        let host_ipa_limit = kvm.get_host_ipa_limit();
+
+        if host_ipa_limit > 0 {
+            assert!(host_ipa_limit >= 32);
+        } else {
+            // if unsupported, the return value should be 0.
+            assert_eq!(host_ipa_limit, 0);
+        }
+    }
+
     #[test]
     fn test_kvm_getters() {
         let kvm = Kvm::new().unwrap();