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| From: | Paolo Bonzini |
| Subject: | Re: [Qemu-devel] Exporting kvm_max_guest_tsc_khz to userspace (was Re: [PATCH 4/4] kvm: Allow migration with invtsc) |
| Date: | Mon, 9 Jan 2017 15:58:11 +0100 |
| User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 |
On 08/01/2017 21:28, Eduardo Habkost wrote: >> Well just export KVM_GET_TSC_KHZ in a QMP command right? Its pretty >> easy. >> >> Let me know if you need any help coding or testing. > I just found out that KVM doesn't provide something that QEMU and > libvirt need: the value of kvm_max_guest_tsc_khz. Without it, we > have no way to know if a given VM is really migratable to a host. > > Could we add a KVM_CAP_MAX_TSC_KHZ capability for that? The ratio is really quite high, 256x the host frequency for AMD and 65536x for Intel. Anything below 2^32 Hz (above that, there would probably be other failures) is safe. Paolo
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