arch, vmm: Fix riscv64 build gaps

Several riscv64 paths are compiled by the KVM build but missed
imports or cfg coverage needed by the current code.

Import the vm-memory Bytes trait for the RISC-V UEFI loader, keep
Instant available for migration timing code, and enable the UEFI flash
error path for riscv64.

Assisted-by: OpenAI-Codex:GPT-5

Signed-off-by: wangyf0611 <wangyufeng@iscas.ac.cn>

arch/src/riscv64/uefi.rs

@@ -7,7 +7,7 @@ use std::os::fd::AsFd;
 use std::result;
 
 use thiserror::Error;
-use vm_memory::{GuestAddress, GuestMemory};
+use vm_memory::{Bytes, GuestAddress, GuestMemory};
 
 /// Errors thrown while loading UEFI binary
 #[derive(Debug, Error)]

vmm/src/lib.rs

@@ -12,9 +12,7 @@ use std::panic::AssertUnwindSafe;
 use std::path::PathBuf;
 use std::sync::mpsc::{Receiver, RecvError, SendError, Sender};
 use std::sync::{Arc, Mutex};
-use std::time::Duration;
+use std::time::{Duration, Instant};
-#[cfg(not(target_arch = "riscv64"))]
-use std::time::Instant;
 use std::{io, result, thread};
 
 use anyhow::{Context, anyhow};

vmm/src/memory_manager.rs

@@ -24,7 +24,7 @@ use anyhow::anyhow;
 use arch::RegionType;
 #[cfg(target_arch = "x86_64")]
 use devices::ioapic;
-#[cfg(target_arch = "aarch64")]
+#[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
 use hypervisor::HypervisorVmError;
 use libc::_SC_NPROCESSORS_ONLN;
 use log::{debug, error, info, warn};
@@ -445,7 +445,7 @@ pub enum Error {
     #[error("Failed to allocate MMIO address")]
     AllocateMmioAddress,
 
-    #[cfg(target_arch = "aarch64")]
+    #[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
     /// Failed to create UEFI flash
     #[error("Failed to create UEFI flash")]
     CreateUefiFlash(#[source] HypervisorVmError),