[bhyve][arm64] Number of allowed vcpus

[Mihai Carabas]

On Wed, Jan 13, 2021 at 4:55 PM Rodney W. Grimes <
freebsd-rwg at gndrsh.dnsmgr.net> wrote:

> > Hello,
> >
> > >From my perspective bhyve should use what is stated in the device tree
> if
> > no parameter is given and throw an error when N is greater than the
> device
> > tree value.
> >
> > Mihai
>
> That seems to be one reasonable solution.  I am not very informed on what
> the CPU over commit situation is on an ARM cpu with respect to
> virtualization.
>
> I would also propose as an alternative to just do what was asked by the
> user, which is the current amd64 implementation, OR do as asked and
> emmit a warning message.
>
> I would ask given what was said above: isnt this the same situation as
> if the sum of all VM VCPU's is more than the total cores in the system?
> That is a very common situation, and one we must not restrict.
>

We are talking here about the device tree of the guest. If you boot up a
guest with a device tree of X vcpus, why specify something else on the
command line?

>
> > On Wed, Jan 13, 2021 at 1:55 PM Andrei Martin <
> andrei.cos.martin at gmail.com>
> > wrote:
> >
> > > Hello,
> > >
> > > While working on enabling multiple virtual cpus for the arm64 virtual
> > > machine
> > > I used the bhyve's "-c N" parameter to create N cpus (it gets only the
> > > cpus, in contrast to the amd64). If N is smaller than the number of
> cores
> > > described in the device tree it will enable only N and if it's larger
> it
> > > will enable only the number of cores from the device tree.
> > >
> > > I don't know if it is the best approach. Another way would be to enable
> > > all the cpus from the device tree, no more, no less.
> > >
> > > Do you have any suggestions?
> > >
> > > Andrei
> > >
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>
> --
> Rod Grimes
> rgrimes at freebsd.org
>