riscv64: Introduce fam-wrappers feature

Implement `fam-wrappers` to get hold on `kvm_reg_list` over RISC-V
platforms.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

Author: RuoqingHe

src/lib.rs

@@ -8,7 +8,7 @@
 #![allow(non_snake_case)]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 
-#[cfg(all(feature = "fam-wrappers", not(target_arch = "riscv64")))]
+#[cfg(feature = "fam-wrappers")]
 #[macro_use]
 extern crate vmm_sys_util;
 

src/riscv64/fam_wrappers.rs

@@ -0,0 +1,49 @@
+// Copyright 2024 © Institute of Software, CAS. All rights reserved.
+// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use vmm_sys_util::fam::{FamStruct, FamStructWrapper};
+
+use riscv64::bindings::*;
+
+// There is no constant in the kernel as far as the maximum number
+// of registers on RISC-V, but KVM_GET_REG_LIST usually returns around 160.
+const RISCV64_REGS_MAX: usize = 200;
+
+// Implement the FamStruct trait for kvm_reg_list.
+generate_fam_struct_impl!(kvm_reg_list, u64, reg, u64, n, RISCV64_REGS_MAX);
+
+// Implement the PartialEq trait for kvm_reg_list.
+impl PartialEq for kvm_reg_list {
+    fn eq(&self, other: &kvm_reg_list) -> bool {
+        // No need to call entries's eq, FamStructWrapper's PartialEq will do it for you
+        self.n == other.n
+    }
+}
+
+/// Wrapper over the `kvm_reg_list` structure.
+///
+/// The `kvm_reg_list` structure contains a flexible array member. For details check the
+/// [KVM API KVM_GET_REG_LIST](https://docs.kernel.org/virt/kvm/api.html#kvm-get-reg-list)
+/// documentation. To provide safe access to the array elements, this type is
+/// implemented using [FamStructWrapper](../vmm_sys_util/fam/struct.FamStructWrapper.html).
+pub type RegList = FamStructWrapper<kvm_reg_list>;
+
+#[cfg(test)]
+mod tests {
+    use super::RegList;
+
+    #[test]
+    fn test_reg_list_eq() {
+        let mut wrapper = RegList::new(1).unwrap();
+        assert_eq!(wrapper.as_slice().len(), 1);
+
+        let mut wrapper2 = wrapper.clone();
+        assert!(wrapper == wrapper2);
+
+        wrapper.as_mut_slice()[0] = 1;
+        assert!(wrapper != wrapper2);
+        wrapper2.as_mut_slice()[0] = 1;
+        assert!(wrapper == wrapper2);
+    }
+}

src/riscv64/mod.rs

@@ -5,5 +5,9 @@
 #[allow(clippy::all)]
 #[allow(clippy::undocumented_unsafe_blocks)]
 pub mod bindings;
+#[cfg(feature = "fam-wrappers")]
+pub mod fam_wrappers;
 
 pub use self::bindings::*;
+#[cfg(feature = "fam-wrappers")]
+pub use self::fam_wrappers::*;