[libvirt] [RFC] Question regarding the validity of QEMU capabilities

Marc Hartmayer mhartmay at linux.vnet.ibm.com
Fri Oct 20 11:15:41 UTC 2017

On Fri, Oct 20, 2017 at 01:10 PM +0200, Pavel Hrdina <phrdina at redhat.com> wrote:
> On Fri, Oct 20, 2017 at 12:59:51PM +0200, Marc Hartmayer wrote:
>> Hi all,
>> the actual capabilities of QEMU are depending on the host. This
>> includes dependencies like which kernel modules are loaded or which
>> kernel parameters are used (e.g. kvm.nested). Therefore, after a
>> restart we cannot be sure that the QEMU capabilities remain the same.
>> How can we solve this problem?
> Hi,
> thanks for bringing up this issue, we kind of already know about it
> but it's good idea to discuss it publicly.
>> I have come up with two ways:
>>  - reprobe the capabilities with every host reboot
> This is the solution that was agreed on but nobody was motivated enough
> to write the code :).

First - thank you for the quick answer :)

Would it be okay if the solution depends on systemd?

>>  - check for every possible change in virQEMUCapsIsValid... (this is
>>    already done for KVM). In my opinion this is not the way to go.
> Pavel
Beste Grüße / Kind regards
   Marc Hartmayer

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