[libvirt] [PATCH v3 libvirt 3/3] qemu: add support for MTP filesystem
Eric Blake
eblake at redhat.com
Wed Aug 20 12:40:29 UTC 2014
On 08/20/2014 05:46 AM, Michal Privoznik wrote:
> On 19.08.2014 22:11, Giuseppe Scrivano wrote:
>> Generate the qemu command line option:
>>
>> -device 'usb-mtp,root=$SRC,desc=$TARGET'
>>
>> from the definition XML:
>>
>> <filesystem type='mount'>
>> <source dir='$SRC'/>
>> <target dir='$TARGET'/>
>> <model type='mtp'/>
>> </filesystem>
>>
>> Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1121781
>>
>> Signed-off-by: Giuseppe Scrivano <gscrivan at redhat.com>
>> ---
>> + virBufferAddLit(&opt, "usb-mtp");
>> + virBufferAsprintf(&opt, ",root=%s,desc=%s", fs->src,
>> fs->dst);
>
> Reading qemu sources the root property is called 'x-root'. And indeed
> domain fails to start:
Ouch. Qemu has explicitly documented that anything starting with x- is
unstable, and may change. We probably should NOT be targetting this in
libvirt API just yet, in case qemu changes their mind. It's nice that
you've done the patch as a proof of concept, but I don't think we want
it in the tree yet :(
>
> usb: mtp: tag root property as experimental
>
> Reason: we don't want commit to that interface yet. Possibly
> the implementation will be switched over to use fsdev.
>
> Suggested-by: Paolo Bonzini <pbonzini at redhat.com>
> Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
>
> diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
> index 1b51a90..384d4a5 100644
> --- a/hw/usb/dev-mtp.c
> +++ b/hw/usb/dev-mtp.c
> @@ -1090,7 +1090,7 @@ static const VMStateDescription vmstate_usb_mtp = {
> };
>
> static Property mtp_properties[] = {
> - DEFINE_PROP_STRING("root", MTPState, root),
> + DEFINE_PROP_STRING("x-root", MTPState, root),
> DEFINE_PROP_STRING("desc", MTPState, desc),
> DEFINE_PROP_END_OF_LIST(),
> };
>
>
> Question that pops up immediately: do we want to commit to something
> that even qemu developers don't believe yet? What will happen when qemu
> decides to switch to 'root' attribute again? Libvirt will have to adapt
> which won't work with older qemus supporting 'x-root' only.
Yep - anything in qemu with x- is not a candidate for libvirt support
(for the longest time, we refused to support RDMA migration because it
still had an x- prefix).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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