[libvirt] virDomainGetVcpus error with Fedora 10

Kaitlin Rupert kaitlin at linux.vnet.ibm.com
Thu Mar 19 23:08:02 UTC 2009

>>>>> I tracked this down, and it's failing the if (cpumaps != NULL && 
>>>>> maplen < 1) check in libvirt.c because cpumaps is non-NULL.  Which 
>>>>> is very strange because I'm definitely passing a NULL value.
>>>> The qemud/remote.c helper for the virDomainGetVcpus method is just 
>>>> doing a totally bogus calculation/allocation for the cpumaps field.
>>>> It needs fixing somehow, but I'm not sure how yet
>>> Any update on this?
>> I've had another look at it, and believe I have a suitable fix. There 
>> were
>> two problems.
>>  - Not allocating a large enough array for the cpumaps field
>>  - Not respecting a cpumaplen=0, as meaning pass cpumaps=NULL
>> The latter is what was causing the error message you saw I believe. Can
>> you try the following patch
> +1 (although, i think this is already upstream, sorry for the slow 
> response).
> I am seeing a new issue now.  After calling 
> virDomainSetSchedulerParameters() on a KVM guest, virDomainGetVcpus() 

Oops, the virDomainSetSchedulerParameters() here was a typo.

Anyway, I tracked this issue down to a conflicting install of libvirt on 
the system.  After removing all versions of libvirt and reinstalling, 
this is no longer any issue.

Kaitlin Rupert
IBM Linux Technology Center
kaitlin at linux.vnet.ibm.com

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