This archive includes a 6.5-rc3 kernel and Gentoo Linux userspace configured for RISC-V to enable development and testing of RVV optimizations to OSS projects.
This setup has been tested with qemu-8.0.3. To boot the VM simply run:
$ ./start.sh
There are two accounts available on the system, root and negge. Both have the same password: rise
At boot, the VM starts sshd on port 22. The start.sh script includes a setting to map host port 10000 to VM port 22. You can ssh in with the user account:
$ ssh -p 10000 negge@localhost
This machine has the latest developer tools installed. The following packages are built for RISC-V and available to use:
| Package | Release Date |
|---|---|
| bison-3.8.2 | 2021-9-21 |
| clang-16.0.6 | 2023-6-14 |
| cmake-3.27.1 | 2023-7-25 |
| flex-2.6.4 | 2022-9-24 |
| gcc-13.2.0 | 2023-7-27 |
| git-2.41.0 | 2023-6-1 |
| make-4.4.1 | 2023-2-26 |
| ninja-1.11.1 | 2022-8-30 |
| openssl-3.1.1 | 2023-5-30 |
| python-3.12.0_beta4_p1 | 2023-7-11 |
| rust-1.71.0 | 2023-7-12 |
There are two programs in the negge user directory:
$ ls test
hwcap hwcap.c testrvv testrvv.as testrvv.o
- The
hwcapprogram tests that the 'V' bit is set by getauxval(AT_HWCAP) - The
testrvvprogram executes the vsetvli instruction and returns
These can be used to confirm that the 6.5-rc3 kernel is properly built with CONFIG_RISCV_ISA_V=y and CONFIG_RISCV_ISA_V_DEFAULT_ENABLE=y.
It is possible to use qemu-binfmt to mount and run the system in a chroot. This
has the advantage of using the host kernel and MMU and is significantly faster.
If you have not set up binfmt_misc before, see the section Setting up
binfmt_misc.
As root, configure and start the qemu-binfmt service. You can confirm this is
done correctly with:
$ cat /proc/sys/fs/binfmt_misc/qemu-riscv64
enabled
interpreter /usr/bin/qemu-riscv64
...
The VM already contains a staticly compiled x86_64 QEMU user binary with the patch from [1] backported to qemu-8.0.3 at:
/usr/bin/qemu-riscv64
To create the chroot, run the following commands as root:
mount -o loop,offset=1048576 gentoo.img /mnt/gentoo
cp /etc/resolv.conf /mnt/gentoo/etc
mount --bind /proc /mnt/gentoo/proc
mount --bind /sys /mnt/gentoo/sys
mount --bind /dev /mnt/gentoo/dev
mount --bind /dev/pts /mnt/gentoo/dev/pts
mount --bind /dev/shm /mnt/gentoo/dev/shm
You can enter the chroot with:
chroot /mnt/gentoo /bin/bash
env-update && source /etc/profile
Using the chroot is recommend for building and installing new packages into the VM with the emerge command.
Note, there are some differences between a qemu-user chroot and qemu-system
- The host kernel is still
x86_64so/proc/cpuinfowill not show the RISC-V ISA extensions - Process concurrency is handled by the host kernel
For this reason it is recommended to develop and test RVV optimizations in the emulated VM.
[1] https://gitlab.com/qemu-project/qemu/-/issues/1793
The way in which binfmt_misc is set up depends on the system that is used, but
requires root access in all cases.
At the end of this, the binfmt_misc entry for qemu-riscv64 will point to the
path that is expected in the chroot. The entry will also point to a standard
installation path for the QEMU binaries.
It is assumed that the QEMU interpreter required is the one installed from the package manager.
sudo apt install qemu-user-static
The path to the interpreter stored in binfmt_misc then points to a symlink,
where we want to point to the actual interpreter.
sudo apt install binfmt-support
sudo sed -i 's|interpreter .*|interpreter /usr/bin/qemu-riscv64-static|' /usr/share/binfmts/qemu-riscv64
sudo update-binfmts --importdir /usr/share/binfmts --import qemu-riscv64
cat /proc/sys/fs/binfmt_misc/qemu-riscv64
# enabled
# interpreter /usr/bin/qemu-riscv64-static
# ...
You should now be able to follow the remaining instructions from the previous section to launch the chroot.