There're three parts:

1. riscv-gnu-toolchain installation
2. qemu installation
3. build xv6-riscv

Part1: riscv-gnu-toolchain installation

Env: macOS Catalina 10.15.7

Step1:

git clone --recursive https://github.com/riscv/riscv-gnu-toolchain

Although it doesn't need --recursive in README, this issue still happened on mac.

Step2:

brew install python3 gawk gnu-sed gmp mpfr libmpc isl zlib expat

Step3:

cd riscv-gnu-toolchain
./configure --prefix=/opt/riscv --enable-multilib

To build either cross-compiler with support for both 32-bit and 64-bit

Step4: find your .zshrc, append this line

export PATH="$PATH:/opt/riscv/bin"

and then

source .zshrc

Part2: qemu installation

After installing riscv-gnu-toolchain, I chose to building qemu for macOS first and installed qemu.

Step 1: install prerequisites

brew install libffi gettext glib pkg-config autoconf automake pixman ninja

Explained

Step2: pull the source of qemu

curl -L https://download.qemu.org/qemu-5.2.0.tar.xz > qemu-5.2.0.tar.xz

(why qemu 5.2.0)

Step3: unzip

tar xf qemu-5.2.0.tar.xz

Step4: build and install qemu

cd qemu-5.2.0

and

mkdir build && cd build
../confgiure`
make
make install

Part3: build xv6-riscv

After installing qemu sucessfully, let's start to build xv6-riscv

Step1: Pull the source of xv6-riscv

git clone git://github.com/mit-pdos/xv6-riscv-fall19.git

NOTE: The xv6-riscv-fall19 repository differs slightly from the book's xv6-riscv in order to make the labs easier.

Step2:

cd xv6-riscv-fall19

and

make
make qemu

That's it!
Thanks for your reading~