I've set up a noble container and in there was driving riscv64 emulation as instructed following https://wiki.ubuntu.com/RISC-V/QEMU
Then in that guest I did updates and installed the test workload: $ sudo apt update $ sudo apt upgrade $ sudo apt install build-essential unzip $ wget https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/2095169/+attachment/5852451/+files/repro.zip ubuntu@ubuntu:~$ unzip repro.zip Archive: repro.zip inflating: Makefile inflating: sigill.S inflating: test.c ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc make: *** [Makefile:7: check] Illegal instruction (core dumped This crashed the program in the guest, but not the guest itself. It was 100% reproducible on each try. Update on the host to the version from proposed root@n-lp2095169:~# apt install qemu-block-extra/noble-proposed qemu-system-common/noble-proposed qemu-system-data/noble-proposed qemu-system-gui/noble-proposed qemu-system-misc/noble-proposed qemu-system-modules-opengl/noble-proposed qemu-system-modules-spice/noble-proposed qemu-utils/noble-proposed Reading package lists... Done Building dependency tree... Done Reading state information... Done Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-block-extra' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-system-common' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [all]) for 'qemu-system-data' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-system-gui' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-system-misc' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-system-modules-opengl' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-system-modules-spice' Selected version '1:8.2.2+ds-0ubuntu1.6' (Ubuntu:24.04/noble-proposed [amd64]) for 'qemu-utils' Suggested packages: samba vde2 The following packages will be upgraded: qemu-block-extra qemu-system-common qemu-system-data qemu-system-gui qemu-system-misc qemu-system-modules-opengl qemu-system-modules-spice qemu-utils 8 upgraded, 0 newly installed, 0 to remove and 59 not upgraded. Need to get 63.7 MB of archives. After this operation, 135 kB disk space will be freed. Get:1 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-modules-spice amd64 1:8.2.2+ds-0ubuntu1.6 [70.2 kB] Get:2 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-modules-opengl amd64 1:8.2.2+ds-0ubuntu1.6 [183 kB] Get:3 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-gui amd64 1:8.2.2+ds-0ubuntu1.6 [314 kB] Get:4 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-block-extra amd64 1:8.2.2+ds-0ubuntu1.6 [111 kB] Get:5 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-utils amd64 1:8.2.2+ds-0ubuntu1.6 [2220 kB] Get:6 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-misc amd64 1:8.2.2+ds-0ubuntu1.6 [57.7 MB] Get:7 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-common amd64 1:8.2.2+ds-0ubuntu1.6 [1252 kB] Get:8 http://archive.ubuntu.com/ubuntu noble-proposed/main amd64 qemu-system-data all 1:8.2.2+ds-0ubuntu1.6 [1790 kB] Fetched 63.7 MB in 7s (8810 kB/s) (Reading database ... 52709 files and directories currently installed.) Preparing to unpack .../0-qemu-system-modules-spice_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-system-modules-spice (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../1-qemu-system-modules-opengl_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-system-modules-opengl (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../2-qemu-system-gui_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-system-gui (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../3-qemu-block-extra_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-block-extra (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../4-qemu-utils_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-utils (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../5-qemu-system-misc_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-system-misc (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../6-qemu-system-common_1%3a8.2.2+ds-0ubuntu1.6_amd64.deb ... Unpacking qemu-system-common (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Preparing to unpack .../7-qemu-system-data_1%3a8.2.2+ds-0ubuntu1.6_all.deb ... Unpacking qemu-system-data (1:8.2.2+ds-0ubuntu1.6) over (1:8.2.2+ds-0ubuntu1.5) ... Setting up qemu-system-common (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-system-data (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-utils (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-block-extra (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-system-misc (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-system-modules-opengl (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-system-gui (1:8.2.2+ds-0ubuntu1.6) ... Setting up qemu-system-modules-spice (1:8.2.2+ds-0ubuntu1.6) ... Processing triggers for man-db (2.12.0-4build2) ... Processing triggers for hicolor-icon-theme (0.17-2) ... root@n-lp2095169:~# dpkg -l | grep '\sqemu-' ii qemu-block-extra 1:8.2.2+ds-0ubuntu1.6 amd64 extra block backend modules for qemu-system and qemu-utils ii qemu-system-common 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU full system emulation binaries (common files) ii qemu-system-data 1:8.2.2+ds-0ubuntu1.6 all QEMU full system emulation (data files) ii qemu-system-gui 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU full system emulation binaries (graphical display and audio modules) ii qemu-system-misc 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU full system emulation binaries (miscellaneous) ii qemu-system-modules-opengl 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU full system emulation binaries (OpenGL display modules) ii qemu-system-modules-spice 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU full system emulation binaries (spice display modules) ii qemu-utils 1:8.2.2+ds-0ubuntu1.6 amd64 QEMU utilities Then starting the guest again root@n-lp2095169:~# qemu-system-riscv64 -machine virt -nographic -m 2048 -smp 4 -bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf -device virtio-net- device,netdev=eth0 -netdev user,id=eth0,hostfwd=tcp::6666-:22 -drive file=/root/ubuntu-24.04.1-preinstalled-server- riscv64.img,format=raw,if=virtio And in the guest run the test workload with the updated qemu: Hrm, at least to me that does not change a thing ... :-/ ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc make: *** [Makefile:7: check] Illegal instruction (core dumped) Re-reading and realizing in comment 5 that I might need to add `-cpu max` to the command line to expose the offending half implemented instruction n the first place. Ok, now this works reliably ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc Which means I have to downgrade qemu again to ensure this was broken before the fix. root@n-lp2095169:~# v=1:8.2.2+ds-0ubuntu1.5; apt install qemu-block-extra=$v qemu-system-common=$v qemu-system-data=$v qemu-system-gui=$v qemu-system-misc=$v qemu-system-modules-opengl=$v qemu-system-modules-spice=$v qemu-utils=$v ... root@n-lp2095169:~# qemu-system-riscv64 -machine virt -cpu max -nographic -m 2048 -smp 4 -bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf -device virtio-net-device,netdev=eth0 -netdev user,id=eth0,hostfwd=tcp::6666-:22 -drive file=/root/ubuntu-24.04.1-preinstalled-server-riscv64.img,format=raw,if=virtio ... ubuntu@ubuntu:~$ make gcc -g -march=rv64gcv test.c sigill.S -o test ./test abc abc make: *** [Makefile:7: check] Illegal instruction (core dumped) Ok, so all was fine, just the test instructions should mention the cpu type. I'll add that and set verification done ** Tags removed: verification-needed verification-needed-noble ** Tags added: verification-done verification-done-noble ** Description changed: [ Impact ] * Qemu 8.2.2 claims to support the riscv64 vector extension, but fails to set the emulated vstart_eq_zero flag, which then causes illegal instruction crashes in certain cases. * Launchpad builders currently use the same Qemu package as Noble, so this SRU will be the basis for fixing our riscv64 builds for future Ubuntu versions. * This was reported upstream (https://gitlab.com/qemu-project/qemu/-/issues/1976) and fixed in Qemu 9.0, so please backport the fix linked in the issue. [ Test Plan ] * I've attached some code which can reproduce the issue. - * Reproduction requires running a riscv64 Noble image, via Qemu system emulation, on an amd64 host; see instructions in https://wiki.ubuntu.com/RISC-V/QEMU + * Reproduction requires running a riscv64 Noble image, via Qemu system emulation, on an amd64 host; see instructions in https://wiki.ubuntu.com/RISC-V/QEMU but to expose the half way implemented instruction one needs to also add -cpu max * Boot up the VM, transfer the necessary files over, `apt install build-essential unzip`, then unzip the reproduction files and compile & run the test (within the VM) with `make`. [ Where problems could occur ] * All changes would be restricted to target/riscv in the Qemu tree, so other architectures shouldn't be affected at all. Furthermore, fixes should only affect vector instructions. * Possible problems range from build failures to riscv emulation failing completely, but the test above covers those cases. [ Other Info ] * Relevant MR: https://code.launchpad.net/~baioc/ubuntu/+source/qemu/+git/qemu/+merge/479676 - * PPA for testing: https://launchpad.net/~baioc/+archive/ubuntu/qemu-sru-riscv-vstart-eq-zero + * PPA for testing: https://launchpad.net/~baioc/+archive/ubuntu/qemu-sru-riscv-vstart-eq-zero -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2095169 Title: [SRU] SIGILL on emulation of RISC-V Vector instructions To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/2095169/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
