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Hi Seong,

The runtime's virtcontainers package uses the govmm package [1] for clock handling. Although govmm provides the facility you want [2], the Kata runtime doesn't currently allow you to modify the clock [3] (since it is unusual to _not_ want the VM clock to be synchronised with the host).

Please raise an issue [4] so the idea can be discussed further so we can understand your use-case better (and let us know if you'd be prepared to help ;)

______

Note: This is *not* recommended, but if you _really_ want to change the clock and you fully understand the consequences, you could use the following non-invasive interpositioning trick:

1) Create a shell script (let's call it "qemu.sh") that:

- Reads all its cli arguments.
- Replaces the clock arguments with those that you want.
- Calls "exec /real/path/to/qemu/binary "$new_set_of_args" to launch the hypervisor with the modified options.

2) Change your configuration.toml to set hypervisor.qemu.path = "/path/to/qemu.sh"

Cheers,

James

[1] - https://github.com/kata-containers/govmm
[2] - https://github.com/kata-containers/govmm/blob/master/qemu/qemu.go#L2169..L2178
[3] - https://github.com/kata-containers/kata-containers/blob/main/src/runtime/virtcontainers/qemu.go#L547..L551
[4] - https://github.com/kata-containers/kata-containers/issues/new/choose
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________________________________________
De : 문성 <seong at etri.re.kr>
Envoyé : jeudi 27 mai 2021 10:29
À : kata-dev at lists.katacontainers.io
Objet : [kata-dev] how to configure kata VM's RTCClock ?

It seems like the kata-runtime runs a VM's clock mode as host as default. It makes the VM's clock synchronize to the clock of host machine. On host, VM runs with this qemu parameters.
     /usr/bin/qemu-vanilla-system-x86_64 …  -rtc base=utc,driftfix=slew,clock=host

But, I'd like to configure the VM RTCClock as vm not host.
I've looked into the /usr/share/defaults/kata-containers/configuration.toml file. But I can't find any field which I can configure the RTCClock.

Are there any way to configure the VM's RTCClock in kata container ?
Or, Is there any reason that you wouldn't include configuration option for the RTCClock ?

regards.
seong.


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