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Re: [libvirt] [PATCH] qemu: Remove limit enforcing when setting processor count

On 09/07/2012 06:51 AM, Peter Krempa wrote:
> When setting processor count for a domain using the API libvirt enforced
> a maximum processor count that was determined using an IOCTL on
> /dev/kvm. Unfortunately this value isn't representative enough and qemu
> happily accepts and starts with values greater than the reported value.

But isn't there still _some_ reasonable limit that we should be
checking?  That is, although qemu will let me run a guest with 3 vcpus
on my 2-cpu laptop, I'm sure that even qemu will reject an attempt to
run 1000000 vcpus - how do we know what the real limit is?

Also, I'm a bit worried that we may have other places in our code that
might need fixing if vcpus > max pcpus, but I guess we'll discover those
as we go along.

As to the patch itself, the code looks fine; and since it only relaxes
constraints, I think it is safe to apply; I'm just worried that we are
relaxing too far, so you might want to wait for a second opinion or
research further into the max limit enforced by qemu.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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