[libvirt] How to detect if qemu supports discard?

Richard W.M. Jones rjones at redhat.com
Sun Mar 9 15:23:25 UTC 2014


from src/qemu/qemu_command.c:

    if (disk->discard) {
        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DRIVE_DISCARD)) {
            virBufferAsprintf(&opt, ",discard=%s",
                              virDomainDiskDiscardTypeToString(disk->discard));
        } else {
            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                           _("discard is not supported by this QEMU binary"));
            goto error;
        }
    }

However there appears to be no way to tell programmatically if the
qemu binary supports discard (ie. via libvirt).  Therefore libguestfs
can never know when it is safe to use this option in the XML.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org




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