diff --git a/libs/hyp/src/error.rs b/libs/hyp/src/error.rs
new file mode 100644
index 0000000..20a0cff
--- /dev/null
+++ b/libs/hyp/src/error.rs
@@ -0,0 +1,45 @@
+// Copyright 2023, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Error and Result types for hypervisor.
+
+use core::{fmt, result};
+
+/// Result type with hypervisor error.
+pub type Result<T> = result::Result<T, Error>;
+
+/// Hypervisor error.
+#[derive(Debug, Clone)]
+pub enum Error {
+    /// MMIO guard is not supported.
+    MmioGuardNotsupported,
+    /// Failed to invoke a certain HVC function.
+    HvcError(smccc::Error, u32),
+    /// The MMIO_GUARD granule used by the hypervisor is not supported.
+    UnsupportedMmioGuardGranule(usize),
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Self::MmioGuardNotsupported => write!(f, "MMIO guard is not supported"),
+            Self::HvcError(e, function_id) => {
+                write!(f, "Failed to invoke the HVC function with function ID {function_id}: {e}")
+            }
+            Self::UnsupportedMmioGuardGranule(g) => {
+                write!(f, "Unsupported MMIO guard granule: {g}")
+            }
+        }
+    }
+}
diff --git a/libs/hyp/src/hypervisor/common.rs b/libs/hyp/src/hypervisor/common.rs
index d1439db..550fb2e 100644
--- a/libs/hyp/src/hypervisor/common.rs
+++ b/libs/hyp/src/hypervisor/common.rs
@@ -14,23 +14,20 @@
 
 //! This module regroups some common traits shared by all the hypervisors.
 
-use smccc::Result;
+use crate::error::Result;
 
 /// Trait for the hypervisor.
 pub trait Hypervisor {
-    /// Returns MMIO guard granule size in bytes.
-    fn mmio_guard_granule(&self) -> Result<usize>;
-
-    /// Registers to use MMIO guard APIs.
+    /// Initializes the hypervisor by enrolling a MMIO guard and checking the memory granule size.
     /// By enrolling, all MMIO will be blocked unless allow-listed with `mmio_guard_map`.
     /// Protected VMs are auto-enrolled.
-    fn mmio_guard_enroll(&self) -> Result<()>;
+    fn mmio_guard_init(&self) -> Result<()>;
 
     /// Maps a memory address to the hypervisor MMIO guard.
-    fn mmio_guard_map(&self, ipa: u64) -> Result<()>;
+    fn mmio_guard_map(&self, addr: usize) -> Result<()>;
 
     /// Unmaps a memory address from the hypervisor MMIO guard.
-    fn mmio_guard_unmap(&self, ipa: u64) -> Result<()>;
+    fn mmio_guard_unmap(&self, addr: usize) -> Result<()>;
 
     /// Shares a region of memory with host, granting it read, write and execute permissions.
     /// The size of the region is equal to the memory protection granule returned by
diff --git a/libs/hyp/src/hypervisor/kvm.rs b/libs/hyp/src/hypervisor/kvm.rs
index cac9ba2..615c75a 100644
--- a/libs/hyp/src/hypervisor/kvm.rs
+++ b/libs/hyp/src/hypervisor/kvm.rs
@@ -15,7 +15,8 @@
 //! Wrappers around calls to the KVM hypervisor.
 
 use super::common::Hypervisor;
-use smccc::{checked_hvc64, checked_hvc64_expect_zero, Error, Result};
+use crate::error::{Error, Result};
+use crate::util::{page_address, SIZE_4KB};
 
 const ARM_SMCCC_KVM_FUNC_HYP_MEMINFO: u32 = 0xc6000002;
 const ARM_SMCCC_KVM_FUNC_MEM_SHARE: u32 = 0xc6000003;
@@ -29,46 +30,43 @@
 pub(super) struct KvmHypervisor;
 
 impl Hypervisor for KvmHypervisor {
-    fn mmio_guard_granule(&self) -> Result<usize> {
-        let args = [0u64; 17];
-
-        let granule = checked_hvc64(VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID, args)?;
-        Ok(granule.try_into().unwrap())
+    fn mmio_guard_init(&self) -> Result<()> {
+        mmio_guard_enroll()?;
+        let mmio_granule = mmio_guard_granule()?;
+        if mmio_granule != SIZE_4KB {
+            return Err(Error::UnsupportedMmioGuardGranule(mmio_granule));
+        }
+        Ok(())
     }
 
-    fn mmio_guard_enroll(&self) -> Result<()> {
-        let args = [0u64; 17];
-
-        checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID, args)
-    }
-
-    fn mmio_guard_map(&self, ipa: u64) -> Result<()> {
+    fn mmio_guard_map(&self, addr: usize) -> Result<()> {
         let mut args = [0u64; 17];
-        args[0] = ipa;
+        args[0] = page_address(addr);
 
         // TODO(b/277859415): pKVM returns a i32 instead of a i64 in T.
         // Drop this hack once T reaches EoL.
         let is_i32_error_code = |n| u32::try_from(n).ok().filter(|v| (*v as i32) < 0).is_some();
-        match checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID, args) {
-            Err(Error::Unexpected(e)) if is_i32_error_code(e) => match e as u32 as i32 {
-                -1 => Err(Error::NotSupported),
-                -2 => Err(Error::NotRequired),
-                -3 => Err(Error::InvalidParameter),
-                ret => Err(Error::Unknown(ret as i64)),
+        match smccc::checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID, args) {
+            Err(smccc::Error::Unexpected(e)) if is_i32_error_code(e) => match e as u32 as i32 {
+                -1 => Err(smccc::Error::NotSupported),
+                -2 => Err(smccc::Error::NotRequired),
+                -3 => Err(smccc::Error::InvalidParameter),
+                ret => Err(smccc::Error::Unknown(ret as i64)),
             },
             res => res,
         }
+        .map_err(|e| Error::HvcError(e, VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID))
     }
 
-    fn mmio_guard_unmap(&self, ipa: u64) -> Result<()> {
+    fn mmio_guard_unmap(&self, addr: usize) -> Result<()> {
         let mut args = [0u64; 17];
-        args[0] = ipa;
+        args[0] = page_address(addr);
 
         // TODO(b/277860860): pKVM returns NOT_SUPPORTED for SUCCESS in T.
         // Drop this hack once T reaches EoL.
-        match checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID, args) {
-            Err(Error::NotSupported) | Ok(_) => Ok(()),
-            x => x,
+        match smccc::checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID, args) {
+            Err(smccc::Error::NotSupported) | Ok(_) => Ok(()),
+            Err(e) => Err(Error::HvcError(e, VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID)),
         }
     }
 
@@ -92,3 +90,27 @@
         Ok(granule.try_into().unwrap())
     }
 }
+
+fn mmio_guard_granule() -> Result<usize> {
+    let args = [0u64; 17];
+
+    let granule = checked_hvc64(VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID, args)?;
+    Ok(granule.try_into().unwrap())
+}
+
+fn mmio_guard_enroll() -> Result<()> {
+    let args = [0u64; 17];
+    match smccc::checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID, args) {
+        Ok(_) => Ok(()),
+        Err(smccc::Error::NotSupported) => Err(Error::MmioGuardNotsupported),
+        Err(e) => Err(Error::HvcError(e, VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID)),
+    }
+}
+
+fn checked_hvc64_expect_zero(function: u32, args: [u64; 17]) -> Result<()> {
+    smccc::checked_hvc64_expect_zero(function, args).map_err(|e| Error::HvcError(e, function))
+}
+
+fn checked_hvc64(function: u32, args: [u64; 17]) -> Result<u64> {
+    smccc::checked_hvc64(function, args).map_err(|e| Error::HvcError(e, function))
+}
diff --git a/libs/hyp/src/lib.rs b/libs/hyp/src/lib.rs
index 676af1d..66c78f4 100644
--- a/libs/hyp/src/lib.rs
+++ b/libs/hyp/src/lib.rs
@@ -16,8 +16,9 @@
 
 #![no_std]
 
+mod error;
 mod hypervisor;
 mod util;
 
+pub use error::{Error, Result};
 pub use hypervisor::{get_hypervisor, Hypervisor};
-pub mod mmio_guard;
diff --git a/libs/hyp/src/mmio_guard.rs b/libs/hyp/src/mmio_guard.rs
deleted file mode 100644
index 84dac64..0000000
--- a/libs/hyp/src/mmio_guard.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-// Copyright 2022, The Android Open Source Project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//! Safe MMIO_GUARD support.
-
-use crate::hypervisor::get_hypervisor;
-use crate::util::{page_address, SIZE_4KB};
-use core::{fmt, result};
-
-/// MMIO guard error.
-#[derive(Debug, Clone)]
-pub enum Error {
-    /// Failed the necessary MMIO_GUARD_ENROLL call.
-    EnrollFailed(smccc::Error),
-    /// Failed to obtain the MMIO_GUARD granule size.
-    GranuleQueryFailed(smccc::Error),
-    /// Failed to MMIO_GUARD_MAP a page.
-    MapFailed(smccc::Error),
-    /// Failed to MMIO_GUARD_UNMAP a page.
-    UnmapFailed(smccc::Error),
-    /// The MMIO_GUARD granule used by the hypervisor is not supported.
-    UnsupportedGranule(usize),
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            Self::EnrollFailed(e) => write!(f, "Failed to enroll into MMIO_GUARD: {e}"),
-            Self::GranuleQueryFailed(e) => write!(f, "Failed to get the MMIO_GUARD granule: {e}"),
-            Self::MapFailed(e) => write!(f, "Failed to MMIO_GUARD map: {e}"),
-            Self::UnmapFailed(e) => write!(f, "Failed to MMIO_GUARD unmap: {e}"),
-            Self::UnsupportedGranule(g) => write!(f, "Unsupported MMIO_GUARD granule: {g}"),
-        }
-    }
-}
-
-/// Result type with mmio_guard::Error.
-pub type Result<T> = result::Result<T, Error>;
-
-/// Initializes the hypervisor by enrolling a MMIO guard and checking the memory granule size.
-pub fn init() -> Result<()> {
-    let hyp = get_hypervisor();
-    hyp.mmio_guard_enroll().map_err(Error::EnrollFailed)?;
-    let mmio_granule = hyp.mmio_guard_granule().map_err(Error::GranuleQueryFailed)?;
-    if mmio_granule != SIZE_4KB {
-        return Err(Error::UnsupportedGranule(mmio_granule));
-    }
-    Ok(())
-}
-
-/// Maps a memory address to the hypervisor MMIO guard.
-pub fn map(addr: usize) -> Result<()> {
-    get_hypervisor().mmio_guard_map(page_address(addr)).map_err(Error::MapFailed)
-}
-
-/// Unmaps a memory address from the hypervisor MMIO guard.
-pub fn unmap(addr: usize) -> Result<()> {
-    get_hypervisor().mmio_guard_unmap(page_address(addr)).map_err(Error::UnmapFailed)
-}