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Re: [libvirt] virDomainGetVcpus error with Fedora 10



Daniel P. Berrange wrote:
On Wed, Mar 11, 2009 at 10:12:16AM -0700, Kaitlin Rupert wrote:
Daniel P. Berrange wrote:
On Fri, Feb 13, 2009 at 03:37:22PM -0800, Kaitlin Rupert wrote:
Hi,

I'm running Fedora 10 with the following libvirt version:  libvirt-0.6.0-3

I'm calling virDomainGetVcpus() with the following parameters: virDomainGetVcpus(dom, info, max, NULL, 0); where max = 2 and dom and info are both non-NULL.

However, I'm getting the following error from libvirt: libvir: Domain error : invalid argument in virDomainGetVcpus

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() returns 0 processors even though virsh dumpxml of the guest shows 3 procs.

Looking at the code for qemudDomainGetVcpus(), maxinfo is set to:

    if (maxinfo > vm->nvcpupids)
        maxinfo = vm->nvcpupids;

I'm passing NULL in for cpumaps, so the whole if (cpumaps != NULL) {} block is skipped, which means the value for vm->nvcpupids is being returned.

Any thoughts?

--
Kaitlin Rupert
IBM Linux Technology Center
kaitlin linux vnet ibm com


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