[libvirt] Cannot find suitable emulator for x86_64

[Mathieu Tarral]

2018-06-14 13:33 GMT+03:00 Daniel P. Berrangé <berrange at redhat.com>:
> On Thu, Jun 14, 2018 at 01:23:56PM +0300, Mathieu Tarral wrote:
>> 2018-06-13 18:23 GMT+03:00 Daniel P. Berrangé <berrange at redhat.com>:
>> > On Wed, Jun 13, 2018 at 06:13:04PM +0300, Mathieu Tarral wrote:
>> >> 2018-06-13 18:07 GMT+03:00 Daniel P. Berrangé <berrange at redhat.com>:
>> >> > On Wed, Jun 13, 2018 at 05:59:37PM +0300, Mathieu Tarral wrote:
>> >> >> >> >
>> >> >> >> > What version of QEMU do you have installed ?  Libvirt has recently
>> >> >> >> > become more aggressive at requiring modern QEMU versions, so its
>> >> >> >> > possible if your old libvirt was running against old QEMU, that
>> >> >> >> > might not be supported with new libvirt.
>> >> >> >>
>> >> >> >> I'm using QEMU 2.8 here.
>> >> >> >> That might explain why libvirt cannot find a version that is modern enough.
>> >> >> >
>> >> >> > 2.8 is plenty new enough, so that's not the issue.
>> >> >>
>> >> >> Alright, so let's focus on libvirt 4.4.0.
>> >> >>
>> >> >> When I start the daemon, i can see some warnings related to QEMU:
>> >> >>
>> >> >> warning : virQEMUCapsInit:942 : Failed to get host CPU cache info
>> >> >> warning : virQEMUCapsInit:949 : Failed to get host power management capabilities
>> >> >>
>> >> >> Could this be the reason, or the beginning of an explanation ?
>> >> >> How can I dig and find what is the root cause ?
>> >> >
>> >> > Best bet is to edit libvirtd.conf and set
>> >> >
>> >> >   log_filters="1:qemu_capabilities"
>> >> >   log_outputs="1:file:/var/log/libvirtd.log"
>> >> >
>> >> > and then rm -rf /var/cache/libvirt/qemu and restart libvirtd. The log
>> >> > file should tell you it is detecting qemu-system-x86_64 and probing it.
>> >> > If anything fails it should be covered in the logs.
>> >>
>> >> Thanks, i have more information now:
>> >>
>> >> debug : virQEMUCapsCacheLookup:4561 : Returning caps (nil) for
>> >> /usr/bin/qemu-system-x86_64
>> >> debug : virQEMUCapsCacheLookup:4561 : Returning caps (nil) for /usr/bin/kvm
>> >>
>> >> Does this help you ?
>> >
>> > No that just says there's no previous capabiltiies stored in the cache,
>> > which is expected since I just told you to delete the cache :-)
>>
>> My bad :D
>>
>> > Please attach the full debug log, after running 'virsh capabilities'
>> Sure.
>> I copy pasted everything in a Github Gist, which is easier to read I think.
>> https://gist.github.com/Wenzel/805558263b7d6d8b3366a684d5673217
>
> Ok this is the key error:
>
> 2018-06-14 10:23:16.994+0000: 31174: error : virCryptoHashBuf:84 : invalid argument: algorithm=1 is not supported
>
> it looks like you've built without gnutls, which is a mandatory dep for
> the QEMU driver.  4.4.0 didn't treat it as mandatory when building, but
> in git master we've fixed that now so you would see the problem sooner.

That was the problem indeed.
I checked out libvirt master (d1605b5d99e847450a6cbbf752ae5dd76239b46f)
and I had to install libgnutls28-dev.

Everything works now:
Compiled against library: libvirt 3.0.0
Using library: libvirt 3.0.0
Using API: QEMU 3.0.0
Running hypervisor: QEMU 2.8.0

I can track down why my call to virDomainIsActive is hanging for no reason :)

Thank you Daniel !

-- 
Mathieu Tarral