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+# Building RISC-V Target with Cmake #
+
+> **Warning**
+> Runtime rvv detection (using `hwcap`) requires linux kernel 6.5 or newer.
+>
+> When running on older kernels, we fall back to compile-time detection, potentially this can cause crashes if rvv is enabled at compile but not supported by the target cpu.
+> Therefore if older kernel support is needed, rvv should be disabled if the target cpu does not support it.
+## Prerequisite: Build RISC-V Clang Toolchain and QEMU ##
+
+If you don't have prebuilt clang and riscv64 qemu, you can refer to the [script](https://github.com/sifive/prepare-riscv-toolchain-qemu/blob/main/prepare_riscv_toolchain_qemu.sh) to get the source. Copy the script to the zlib-ng root directory, and run it to download the source and build them. Modify the content according to your conditions (e.g., toolchain version).
+
+```bash
+./prepare_riscv_toolchain_qemu.sh
+```
+
+After running script, clang & qemu are built in `build-toolchain-qemu/riscv-clang/` & `build-toolchain-qemu/riscv-qemu/`.
+
+`build-toolchain-qemu/riscv-clang/` is your `TOOLCHAIN_PATH`.
+`build-toolchain-qemu/riscv-qemu/bin/qemu-riscv64` is your `QEMU_PATH`.
+
+You can also download the prebuilt toolchain & qemu from [the release page](https://github.com/sifive/prepare-riscv-toolchain-qemu/releases), and enjoy using them.
+
+## Cross-Compile for RISC-V Target ##
+
+```bash
+cmake -G Ninja -B ./build-riscv \
+  -D CMAKE_TOOLCHAIN_FILE=./cmake/toolchain-riscv.cmake \
+  -D CMAKE_INSTALL_PREFIX=./build-riscv/install \
+  -D TOOLCHAIN_PATH={TOOLCHAIN_PATH} \
+  -D QEMU_PATH={QEMU_PATH} \
+  .
+
+cmake --build ./build-riscv
+```
+
+Disable the option if there is no RVV support:
+```
+-D WITH_RVV=OFF
+```
+
+## Run Unittests on User Mode QEMU ##
+
+```bash
+cd ./build-riscv && ctest --verbose
+```