misc: hypervisor: streamline #[source] and Error

This streamlines the code base to follow best practices for
error handling in Rust: Each error struct implements
std::error::Error (most due via thiserror::Error derive macro)
and sets its source accordingly.

This allows future work that nicely prints the error chains,
for example.

So far, the convention is that each error prints its
sub error as part of its Display::fmt() impl.

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

hypervisor/src/arch/aarch64/gic.rs

@@ -17,13 +17,13 @@ use crate::{CpuState, HypervisorDeviceError, HypervisorVmError};
 pub enum Error {
     /// Error while calling KVM ioctl for setting up the global interrupt controller.
     #[error("Failed creating GIC device: {0}")]
-    CreateGic(HypervisorVmError),
+    CreateGic(#[source] HypervisorVmError),
     /// Error while setting device attributes for the GIC.
     #[error("Failed setting device attributes for the GIC: {0}")]
-    SetDeviceAttribute(HypervisorDeviceError),
+    SetDeviceAttribute(#[source] HypervisorDeviceError),
     /// Error while getting device attributes for the GIC.
     #[error("Failed getting device attributes for the GIC: {0}")]
-    GetDeviceAttribute(HypervisorDeviceError),
+    GetDeviceAttribute(#[source] HypervisorDeviceError),
 }
 pub type Result<T> = result::Result<T, Error>;
 

hypervisor/src/arch/emulator/mod.rs

@@ -82,13 +82,13 @@ pub enum EmulationError<T: Debug> {
     WrongNumberOperands(#[source] anyhow::Error),
 
     #[error("Instruction Exception: {0}")]
-    InstructionException(Exception<T>),
+    InstructionException(#[source] Exception<T>),
 
     #[error("Instruction fetching error: {0}")]
     InstructionFetchingError(#[source] anyhow::Error),
 
     #[error("Platform emulation error: {0}")]
-    PlatformEmulationError(PlatformError),
+    PlatformEmulationError(#[source] PlatformError),
 
     #[error(transparent)]
     EmulationError(#[from] anyhow::Error),

hypervisor/src/arch/riscv64/aia.rs

@@ -14,13 +14,13 @@ use crate::{AiaState, HypervisorDeviceError, HypervisorVmError};
 pub enum Error {
     /// Error while calling KVM ioctl for setting up the global interrupt controller.
     #[error("Failed creating AIA device: {0}")]
-    CreateAia(HypervisorVmError),
+    CreateAia(#[source] HypervisorVmError),
     /// Error while setting device attributes for the AIA.
     #[error("Failed setting device attributes for the AIA: {0}")]
-    SetDeviceAttribute(HypervisorDeviceError),
+    SetDeviceAttribute(#[source] HypervisorDeviceError),
     /// Error while getting device attributes for the AIA.
     #[error("Failed getting device attributes for the AIA: {0}")]
-    GetDeviceAttribute(HypervisorDeviceError),
+    GetDeviceAttribute(#[source] HypervisorDeviceError),
 }
 pub type Result<T> = result::Result<T, Error>;
 

hypervisor/src/hypervisor.rs

@@ -67,22 +67,22 @@ pub enum HypervisorError {
     ///
     /// Checking extensions failed
     ///
-    #[error("Checking extensions:{0}")]
+    #[error("Checking extensions: {0}")]
     CheckExtensions(#[source] anyhow::Error),
     ///
     /// Failed to retrieve TDX capabilities
     ///
-    #[error("Failed to retrieve TDX capabilities:{0}")]
+    #[error("Failed to retrieve TDX capabilities: {0}")]
     TdxCapabilities(#[source] anyhow::Error),
     ///
     /// Failed to set partition property
     ///
-    #[error("Failed to set partition property:{0}")]
+    #[error("Failed to set partition property: {0}")]
     SetPartitionProperty(#[source] anyhow::Error),
     ///
     /// Running on an unsupported CPU
     ///
-    #[error("Unsupported CPU:{0}")]
+    #[error("Unsupported CPU: {0}")]
     UnsupportedCpu(#[source] anyhow::Error),
     ///
     /// Launching a VM with unsupported VM Type