Hi KVM communication,
I am working on TSC synchronization between host and guests.
I found this doc (https://docs.kernel.org/virt/kvm/devices/vcpu.html#group-kvm-vcpu-tsc-ctrl), which gives some instructions of how to synchronize them. When I reading the KVM APIs (kernel version 6.4), I am a little confused. It seems to me the KVM APIs don’t match the instructions in the doc.
The doc says "Read the KVM_VCPU_TSC_OFFSET attribute for *every vCPU* to record the guest TSC offset”. However, the KVM API for getting/setting the offset is not through vCPU’s fd, it is through KVM device's fd,
E.g., when I refer to the KVM selftest code, I found accessing TSC_OFFSET is through the “KVM_SET_DEVICE_ATTR” cmd, with args “KVM_VCPU_TSC_CTRL” & “KVM_VCPU_TSC_OFFSET”. It looks like the API sets the TSC offset on all vCPUs, instead of a single vCPU.
Can someone help on it and give some input? Thanks a lot!
Yifei
