Messages in this thread | | | Subject | Re: [patch 0/3] KVM CPU frequency change hypercalls | From | Paolo Bonzini <> | Date | Thu, 23 Feb 2017 18:35:24 +0100 |
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On 03/02/2017 20:09, Radim Krcmar wrote: > One reason why we have a kernel/userspace split is to allow sharing of > CPU time. Each application then its state that the kernel keeps track > of and saves/restores while time-multiplexing. > > Our frequency scaling interface goes against the idea -- guest kernel > cannot schedule multiple userspaces on the same vCPU, because they could > conflict by overriding frequency. > > i.e. our feature implies userspace tasks pinned to isolated vCPUs.
That's bad. This feature is broken by design unless it does proper save/restore across preemption.
You don't need a hypercall. Add a cpufreq driver in DPDK that doesn't use sysfs, and connect it to a daemon in the host through virtio-serial or vsock.
Paolo
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