Bug 1003610

Summary: RFE: capabilities: Expose xen blktap support
Product: [Community] Virtualization Tools Reporter: Cole Robinson <crobinso>
Component: libvirtAssignee: Libvirt Maintainers <libvirt-maint>
Status: CLOSED DEFERRED QA Contact:
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Version: unspecifiedCC: rbalakri
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Last Closed: 2016-03-20 22:26:14 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Cole Robinson 2013-09-02 13:30:37 UTC 
virt-install/virt-manager have had this check forever:

def is_blktap_capable(conn):
    # Ideally we would get this from libvirt capabilities XML
    if conn.is_remote():
        return False

    f = open("/proc/modules")
    lines = f.readlines()
    f.close()
    for line in lines:
        if line.startswith("blktap ") or line.startswith("xenblktap "):
            return True
    return False

If True, we use driver name='tap' for <disk> XML. As the comment above suggestions, libvirt should expose some tag in capabilities so we know a
host supports blktap, and tools don't need to probe lsmod or similar.
Comment 1 Cole Robinson 2016-03-20 22:26:14 UTC 
blktap is apparently not the favored xen driver anymore, as detailed in bug 1171550, so while in theory libvirt should provide this info I don't think anyone practically cares about it anymore.