misc: arch/riscv64: 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

vmm/src/config.rs

@@ -41,81 +41,81 @@ pub enum Error {
     /// Missing restore source_url parameter.
     ParseRestoreSourceUrlMissing,
     /// Error parsing CPU options
-    ParseCpus(OptionParserError),
+    ParseCpus(#[source] OptionParserError),
     /// Invalid CPU features
     InvalidCpuFeatures(String),
     /// Error parsing memory options
-    ParseMemory(OptionParserError),
+    ParseMemory(#[source] OptionParserError),
     /// Error parsing memory zone options
-    ParseMemoryZone(OptionParserError),
+    ParseMemoryZone(#[source] OptionParserError),
     /// Missing 'id' from memory zone
     ParseMemoryZoneIdMissing,
     /// Error parsing rate-limiter group options
-    ParseRateLimiterGroup(OptionParserError),
+    ParseRateLimiterGroup(#[source] OptionParserError),
     /// Error parsing disk options
-    ParseDisk(OptionParserError),
+    ParseDisk(#[source] OptionParserError),
     /// Error parsing network options
-    ParseNetwork(OptionParserError),
+    ParseNetwork(#[source] OptionParserError),
     /// Error parsing RNG options
-    ParseRng(OptionParserError),
+    ParseRng(#[source] OptionParserError),
     /// Error parsing balloon options
-    ParseBalloon(OptionParserError),
+    ParseBalloon(#[source] OptionParserError),
     /// Error parsing filesystem parameters
-    ParseFileSystem(OptionParserError),
+    ParseFileSystem(#[source] OptionParserError),
     /// Error parsing persistent memory parameters
-    ParsePersistentMemory(OptionParserError),
+    ParsePersistentMemory(#[source] OptionParserError),
     /// Failed parsing console
-    ParseConsole(OptionParserError),
+    ParseConsole(#[source] OptionParserError),
     #[cfg(target_arch = "x86_64")]
     /// Failed parsing debug-console
-    ParseDebugConsole(OptionParserError),
+    ParseDebugConsole(#[source] OptionParserError),
     /// No mode given for console
     ParseConsoleInvalidModeGiven,
     /// Failed parsing device parameters
-    ParseDevice(OptionParserError),
+    ParseDevice(#[source] OptionParserError),
     /// Missing path from device,
     ParseDevicePathMissing,
     /// Failed parsing vsock parameters
-    ParseVsock(OptionParserError),
+    ParseVsock(#[source] OptionParserError),
     /// Failed parsing restore parameters
-    ParseRestore(OptionParserError),
+    ParseRestore(#[source] OptionParserError),
     /// Failed parsing SGX EPC parameters
     #[cfg(target_arch = "x86_64")]
-    ParseSgxEpc(OptionParserError),
+    ParseSgxEpc(#[source] OptionParserError),
     /// Missing 'id' from SGX EPC section
     #[cfg(target_arch = "x86_64")]
     ParseSgxEpcIdMissing,
     /// Failed parsing NUMA parameters
-    ParseNuma(OptionParserError),
+    ParseNuma(#[source] OptionParserError),
     /// Failed validating configuration
-    Validation(ValidationError),
+    Validation(#[source] ValidationError),
     #[cfg(feature = "sev_snp")]
     /// Failed parsing SEV-SNP config
-    ParseSevSnp(OptionParserError),
+    ParseSevSnp(#[source] OptionParserError),
     #[cfg(feature = "tdx")]
     /// Failed parsing TDX config
-    ParseTdx(OptionParserError),
+    ParseTdx(#[source] OptionParserError),
     #[cfg(feature = "tdx")]
     /// No TDX firmware
     FirmwarePathMissing,
     /// Failed parsing userspace device
-    ParseUserDevice(OptionParserError),
+    ParseUserDevice(#[source] OptionParserError),
     /// Missing socket for userspace device
     ParseUserDeviceSocketMissing,
     /// Error parsing pci segment options
-    ParsePciSegment(OptionParserError),
+    ParsePciSegment(#[source] OptionParserError),
     /// Failed parsing platform parameters
-    ParsePlatform(OptionParserError),
+    ParsePlatform(#[source] OptionParserError),
     /// Failed parsing vDPA device
-    ParseVdpa(OptionParserError),
+    ParseVdpa(#[source] OptionParserError),
     /// Missing path for vDPA device
     ParseVdpaPathMissing,
     /// Failed parsing TPM device
-    ParseTpm(OptionParserError),
+    ParseTpm(#[source] OptionParserError),
     /// Missing path for TPM device
     ParseTpmPathMissing,
     /// Error parsing Landlock rules
-    ParseLandlockRules(OptionParserError),
+    ParseLandlockRules(#[source] OptionParserError),
     /// Missing fields in Landlock rules
     ParseLandlockMissingFields,
 }