RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

Description of problem:
When we attach a disk to guest with iothread , the iothreadid cannot be 0 , it is invalid.but attach disk won't forbid it.

Version-Release number of selected component (if applicable):
libvirt-1.2.17-4.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. define and start a heathy guest with iothreads,like following :
 <iothreads>4</iothreads>

2. try to attach a disk to guest with iothread = 0 

# virsh attach-disk r7-vm1 /var/lib/libvirt/images/qcow2.img vdb --subdriver qcow2 --iothread 0
Disk attached successfully

chech domain xml , it no iothread in <driver>

#virsh dumpxml r7-vm1 
 <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/qcow2.img'/>
      <backingStore/>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0b' function='0x0'/>
    </disk>

3.using iothreadadd to add iothread id=0 , it is invalid.

# virsh iothreadadd r7-vm1 --id 0
error: Invalid IOThread id value: '0'

Actual results :
As step2 , iothread = 0 can be attached 

Expected resutls :
Libvirt should forbid it .

Additional info :

Hi John, I can reproduce it on libvirt-1.2.17-4.el7.x86_64
Verify it on libvirt-1.2.17-8.el7.x86_64


Steps to Verify:
1. Define a domain which has os, with xml following:
...
<iothreads>4</iothreads>
...
# virsh iothreadinfo t38
 IOThread ID     CPU Affinity   
---------------------------------------------------
 1               0-7
 2               0-7
 3               0-7
 4               0-7

2. Start domain and attach-disk with --iothread 0 option
# virsh start t38                         
Domain t38 started

# virsh attach-disk t38 /var/lib/libvirt/images/test.qcow2 vdb --iothread 0 --config
error: Failed to attach disk
error: XML error: Invalid iothread attribute in disk driver element: 0

virsh attach-disk t38 /var/lib/libvirt/images/test.qcow2 vdb --iothread 0         
error: Failed to attach disk
error: XML error: Invalid iothread attribute in disk driver element: 0

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2202.html