Re: [Qemu-devel] [libvirt] QEMU 1.6 and drive discard parameter

[Gareth Bult <gareth@linux.co.uk>]

Hey guys,

I've just rolled out Qemu 1.6 to fix problems I've been having, which worked fine .. but I've now
lost discard support which is a problem. Is there an easy / quick fix for this without digging through
other people's code? I'm happy to compile up whatever is necessary, I just need the "discard" option 
to work for Libvirt / Qemu 1.6 ...

tia
Gareth.


On Thu, Oct 31, 2013 at 04:35:43PM +0800, Amos Kong wrote:
> On Thu, Oct 31, 2013 at 04:07:15PM +0800, Osier Yang wrote:
> > CC to Amos.
> > 
> > On 30/10/13 16:19, whitearchey wrote:
> > >
> > >In QEMU 1.6 parameters of 'drive' option were removed:
> > >
> > >QemuOptsList qemu_drive_opts = {
> > >    .name = "drive",
> > >    .head = QTAILQ_HEAD_INITIALIZER(qemu_drive_opts.head),
> > >    .desc = {
> > >        /*
> > >         * no elements => accept any params
> > >         * validation will happen later
> > >         */
> > >        { /* end of list */ }
> > >    },
> > >};
> > >
> > >But libvirt still checks for QEMU_CAPS_DRIVE_DISCARD using QMP
> > >query-command-line-options:
> > >
> > >static struct virQEMUCapsCommandLineProps virQEMUCapsCommandLine[] = {
> > >    { "machine", "mem-merge", QEMU_CAPS_MEM_MERGE },
> > >    { "drive", "discard", QEMU_CAPS_DRIVE_DISCARD },
> > >    { "realtime", "mlock", QEMU_CAPS_MLOCK },
> > >};
> > >...
> > >qemuMonitorGetCommandLineOptionParameters(mon,
> > >virQEMUCapsCommandLine[i].option, &values)
> > >
> > >So, when I try to use discard option in domain xml I get this error:
> > >
> > >error : qemuBuildDriveStr:3986 : unsupported configuration:
> > >discard is not supported by this QEMU binary
> > >
> > 
> > It's a qemu problem, the command "query-command-line-options" should
> > keep working
> > after the structures were changed for any option, in this case, all
> > the option descs were
> > moved to "qemu_common_drive_opts" instead.
> 
> { 'execute': 'query-command-line-options', 'arguments': { 'option': 'drive' } 
> }
>  
> {
>     "return": [
>         {
>             "parameters": [
>             ],
>             "option": "drive"
>         }
>     ]
> }
> 
> It returns a NULL parameters list, that's true, some error handling
> should be done by libvirt.