Re: libvirt error - "cannot set CPU affinity"

On 1/31/23 13:43, Dipanjan Das wrote: > Hello, > > I am getting the following error message when trying to run a VM with > the emulatorpin cpuset set to a value - > > "cannot set CPU affinity on process 78: Invalid argument". > > Note that removing the emulatorpin leads to the VM running successfully. > > The core that I am setting for the emulatorpin cpuset is present on the > system and is not in the isolcpus set of the host. The question is, whether the container that libvirtd runs in is allowed to run on the selected cpuset. I mean, you can have a cgroup that allows a subset of physical CPUs, and when a process running within the cgroup tries to set affinity to a CPU that's not allowed it gets EINVAL.

The function this error message comes from is: virProcessSetAffinity() (the linux version) https://gitlab.com/libvirt/libvirt/-/blob/master/src/util/virprocess.c#L445 Another reason for the error might be insufficient permissions (though the man page of sched_setaffinity() says you'd get an EPERM so maybe not). > > Any suggestions on what could be the problem? Any pointers to how to > debug the issue would help greatly too. Turning on debug logs is a good start. From there you'd need a trained eye to see the code path, but if you post a link to the logs here I'll try to help.