On Wed, Jun 18, 2025 at 12:50 PM Heinrich Schuchardt < [email protected]> wrote:
> If I run the dual core inner VM via `taskset 0x03 qemu-system-riscv64 > ...`, the amd64 cores are released while the inner VM idles. But once > the inner VM is stopped the amd64 CPU consumption sticks at 2 CPUs. > > `mpstat -P ALL` provides this output > (https://paste.ubuntu.com/p/5ZDbDqJ86g/): > > > 07:38:56 PM CPU %usr %nice %sys %iowait %irq %soft > %steal %guest %gnice %idle > 07:38:56 PM all 1.66 0.00 2.11 0.04 0.00 0.01 > 0.00 3.53 0.00 92.66 > 07:38:56 PM 0 1.99 0.00 5.88 0.04 0.00 0.01 > 0.00 28.11 0.00 63.98 > 07:38:56 PM 1 6.10 0.00 10.23 0.10 0.00 0.05 > 0.00 28.60 0.00 54.93 > 07:38:56 PM 2 0.89 0.00 1.63 0.01 0.00 0.01 > 0.00 0.00 0.00 97.46 > 07:38:56 PM 3 1.60 0.00 1.40 0.01 0.00 0.01 > 0.00 0.00 0.00 96.98 > 07:38:56 PM 4 0.94 0.01 1.13 0.07 0.00 0.02 > 0.00 0.00 0.00 97.82 > 07:38:56 PM 5 1.17 0.00 0.88 0.05 0.00 0.01 > 0.00 0.00 0.00 97.89 > 07:38:56 PM 6 0.82 0.00 1.04 0.01 0.00 0.01 > 0.00 0.00 0.00 98.12 > 07:38:56 PM 7 0.90 0.00 0.80 0.02 0.00 0.01 > 0.00 0.00 0.00 98.27 > 07:38:56 PM 8 2.50 0.00 1.28 0.03 0.00 0.01 > 0.00 0.00 0.00 96.18 > 07:38:56 PM 9 1.21 0.00 2.25 0.01 0.00 0.01 > 0.00 0.00 0.00 96.52 > 07:38:56 PM 10 0.90 0.00 0.90 0.01 0.00 0.01 > 0.00 0.00 0.00 98.19 > 07:38:56 PM 11 2.06 0.00 1.66 0.18 0.00 0.01 > 0.00 0.00 0.00 96.09 > 07:38:56 PM 12 1.06 0.00 0.98 0.01 0.00 0.01 > 0.00 0.00 0.00 97.94 > 07:38:56 PM 13 0.98 0.00 1.48 0.02 0.00 0.01 > 0.00 0.00 0.00 97.51 > 07:38:56 PM 14 1.81 0.00 1.01 0.02 0.00 0.01 > 0.00 0.00 0.00 97.14 > 07:38:56 PM 15 1.57 0.00 1.25 0.02 0.00 0.02 > 0.00 0.00 0.00 97.14 > > Column %guest shows the percentage of time spent by the CPUs to run a > virtual processor. > > Though the inner VM is stopped the VCPUs don't idle completely. > > Idling is implemented via the `wfi` opcode. Could it be that the cores > assigned to VCPUs still receive abundant interrupts? > > Yeah quite possible. Initially I thought it was a qemu tcg bug so I went down the rabit hole and got distracted with the icount thing. I am looking at KVM vcpu timer code first to see if it is constantly firing timer interrupts for some reason. > -- > You received this bug notification because you are subscribed to the bug > report. > https://bugs.launchpad.net/bugs/2112578 > > Title: > riscv64: KVM does not release harts > > Status in linux package in Ubuntu: > New > Status in qemu package in Ubuntu: > Invalid > > Bug description: > In the 6.14.0-13-generic kernel there seems to be a problem with KVM. > > On my amd64 machine I am running a riscv64 machine using QEMU 10 with > 16 cores. Inside the VM I spin up a further machine with 2 cores. Once > KVM emulation is started the load of my amd64 machine rises to > 14/16 > cores for qemu-system-riscv64. KVM seems not to release cores that > were ever used. Top in 1st VM shows 0.25 cores used for 2nd VM. > > The usage on my amd64 machine only drops when unloading the kvm module > in the first VM. > --- > ProblemType: Bug > ApportVersion: 2.32.0-0ubuntu5 > Architecture: riscv64 > AudioDevicesInUse: > USER PID ACCESS COMMAND > /dev/snd/controlC0: zfsdt 2105 F.... wireplumber > /dev/snd/seq: zfsdt 2103 F.... pipewire > CasperMD5json: > { > "result": "skip" > } > CurrentDesktop: XFCE > DistroRelease: Ubuntu 25.10 > InstallationDate: Installed on 2025-03-17 (80 days ago) > InstallationMedia: Ubuntu-Server 25.04 "Plucky Puffin" - Daily riscv64 > (20250316) > Lsusb: > Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub > Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd QEMU Tablet > Bus 001 Device 003: ID 0627:0001 Adomax Technology Co., Ltd QEMU Tablet > Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub > MachineType: QEMU QEMU Virtual Machine > Package: linux (not installed) > ProcEnviron: > LANG=en_US.UTF-8 > PATH=(custom, no user) > SHELL=/bin/bash > TERM=xterm-256color > ProcFB: 0 virtio_gpudrmfb > ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.14.0-13-generic > root=UUID=af336ba2-ea81-4dd5-bada-b3e8e7fb1c58 ro > crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M > ProcVersionSignature: Ubuntu 6.14.0-13.13.2-generic 6.14.0 > PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No > PulseAudio daemon running, or not running as session daemon. > RelatedPackageVersions: > linux-restricted-modules-6.14.0-13-generic N/A > linux-backports-modules-6.14.0-13-generic N/A > linux-firmware 20250317.git1d4c88ee-0ubuntu1 > RfKill: > > Tags: questing > Uname: Linux 6.14.0-13-generic riscv64 > UpgradeStatus: Upgraded to questing on 2025-05-17 (19 days ago) > UserGroups: N/A > _MarkForUpload: True > acpidump: > > dmi.bios.date: 05/13/2025 > dmi.bios.release: 0.0 > dmi.bios.vendor: Ubuntu distribution of EDK II > dmi.bios.version: 2025.02-8 > dmi.chassis.type: 1 > dmi.chassis.vendor: QEMU > dmi.chassis.version: virt > dmi.modalias: > dmi:bvnUbuntudistributionofEDKII:bvr2025.02-8:bd05/13/2025:br0.0:svnQEMU:pnQEMUVirtualMachine:pvrvirt:cvnQEMU:ct1:cvrvirt:sku: > dmi.product.name: QEMU Virtual Machine > dmi.product.version: virt > dmi.sys.vendor: QEMU > > To manage notifications about this bug go to: > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2112578/+subscriptions > > -- Regards, Atish -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2112578 Title: riscv64: KVM does not release harts To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2112578/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
