Re: Configuring qemu for Vector Extension

Tony Cole

Hi Mick,


I use the RISC-V Vector QEMU branch from SiFive (for 32-bit, don’t know about 64-bit support though):


Also, there may be a later version.



Follow the building instructions in the README.rst.



Hope this helps.






From: tech-vector-ext@... [mailto:tech-vector-ext@...] On Behalf Of Mick Thomas Lim
Sent: 13 September 2021 01:21
To: tech-vector-ext@...
Subject: [RISC-V] [tech-vector-ext] Configuring qemu for Vector Extension


Does a known-good guide exist for building riscv64 qemu to be able to run Vector instructions?


From the main qemu repo, we are to build the riscv64-softmmu target and run the 64-bit Buildroot Image, as described here:


A "Hello World" program compiled with riscv64-unknown-linux-gnu-gcc does work.

But we aren't seeing expected behavior when running the simple rvv_vadd.c program described here:


For example: vl = vsetvl_e32m2 (n) seems to return 0.


This is the qemu run command we're using for buildroot:
qemu-system-riscv64 -cpu rv64,x-v=true,vlen=256,elen=64,vext_spec=v0.7.1    -M virt -nographic    -bios output/images/fw_jump.elf    -kernel output/images/Image    -append "root=/dev/vda ro"    -drive file=output/images/rootfs.ext2,format=raw,id=hd0    -device virtio-blk-device,drive=hd0    -netdev user,id=net0 -device virtio-net-device,netdev=net0


Assistance would much appreciated!




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