On 31.08.2015 22:13, Programmingkid wrote: > > On Aug 29, 2015, at 12:39 PM, Max Reitz wrote: > >> On 29.08.2015 17:57, Programmingkid wrote: >>> >>> On Aug 29, 2015, at 11:40 AM, Max Reitz wrote: >>> >>>> On 27.08.2015 03:05, G 3 wrote: >>>>> I want to share files between my host and guest computer. A feature I >>>>> want to add would be a new menu item in the Machine menu called "Mount >>>>> Image File...". When the user selects it, a file open dialog box >>>>> displays. The user can then select the image file with the file he wants >>>>> to use. After pushing the OK button, the image file would be mounted >>>>> like a USB flash drive. This menu item would only show up if there is >>>>> usb support in the guest machine. >>>>> >>>>> Would you be open to accepting such a feature? >>>> >>>> Generally I'd expect this to be functionality exposed by the management >>>> layer. For instance using virt-manager, this can be achived as follows: >>>> Switch to "Details", then click "Add Hardware", choose "Storage" and >>>> "USB" as the "Bus type". Choose the image, click "Finish", done. >>> >>> Isn't Libvirt only available on Linux? This mount image file feature would >>> only be on Mac OS X. >> >> I'm not sure whether that sounds like a good idea, because then people >> using bare qemu on Linux would complain that it isn't available with >> Gtk. So if this was to be implemented, it would have to implemented >> cross-platform (or at least in a way so it can be used cross-platform >> later on). >> >>> Mac OS X users don't have all the fancy GUI wrappers >>> for QEMU :( >> >> Good thing most GNU/Linux distributions are free. ;-) >> >> (sorry, could not resist) >> >>> Mac OS X is a second-class citizen in the QEMU world... >> >> Might have to do something with most (?) of it being non-free and Apple >> not caring enough about KVM. >> >> (And without KVM, people in turn don't care enough about OS X as a qemu >> host.) >> >> ((But all of that is pretty biased speculation, of course.)) >> >>>> The main problem I see with adding this functionality to qemu itself >>>> would be having to get even further into the GUI business, which hasn't >>>> worked out too well so far… >>> >>> That is because of several reasons. One being maintainers not wanting to >>> advance the GUI because they feel another program should be QEMU's >>> GUI. I'm sure there are plenty of good ideas that would advance QEMU's >>> GUI. These ideas just need to be accepted into QEMU rather than put off. >> >> Another is that some people simply feel that qemu should focus on being >> a backend than having to mess with frontend work, too. See the recent >> discussion on the Gtk code setting the locale and thus breaking QMP for >> an example why they have a point. >> >> I guess you'll better talk to Markus about this. :-) >> >> Quote: "We should've stayed out of the GUI business." >> >> (http://lists.nongnu.org/archive/html/qemu-devel/2015-08/msg03049.html) >> >>>> If we didn't care about that, than we'd have to think about the >>>> implementation. Internally, we'd probably call QMP's blockdev-add to >>>> open the image file, and then QMP's device_add to add the USB device. So >>>> then qemu would use its own management interfaces to execute the >>>> operation, which seems a bit strange to me, further hinting at the fact >>>> that we probably should leave this to the management layer. >>> >>> What works does, and it isn't always as nice looking >>> as we want it. I am sure we will use some kind of API to implement this >>> feature. >> >> Having to deal with ugly legacy cruft from time to time, I don't know >> whether "What works, works" is always appropriate. >> >>> I just wish there were an easy way to share files between the host and the >>> guest. >> >> I don't think using emulated USB storage is the right way to do this, >> though. Stefan is working on file sharing using NFS over virtio-vsock, >> which seems more appropriate. But then again I don't whether >> virtio-vsock will work with an OS X host… >> >> === >> >> OK, if you really want to implement it, I'm certainly not the right one >> to stop you, so here is how I'd do it: >> >> My "BlockBackend and media" series rewrites the "change" HMP/QMP command >> to be a macro, basically, that actually executes four lower-level QMP >> commands. So this means we have a precedent of "macro" QMP commands, and >> this could be extended. So you could add a "macro" QMP command >> "usb-storage-insert-file" or something which executes blockdev-add + >> device_add (if that works).* >> >> Then, if I felt really fancy, I'd add some layer which allows >> generically executing QMP commands through the GUI, based on a whitelist >> of commands. Each parameter would have to be requested through some GUI >> interface, for instance, filenames would be queried through an >> appropriate dialog. Ideally, this would be GUI-agnostic, but this may >> not be reasonably possible. >> >> Then you'd whitelist usb-storage-insert-file (or however it is named), >> give it some nice alias and you'd be done. >> >> While this would be much work I feel like this would actually be the >> nicest solution. >> >> This is just a very rough outline, though, and since it somehow goes >> against everything qemu's GUI was used for so far (just the most basic >> things, basically nothing about controlling the VM except for >> Pause/Shutdown/Reboot) I have no idea how it would be received. >> >> Max >> >> >> *Actually you'd probably want a generic insert-storage-file which takes >> the kind of storage device to add as a parameter. > > I thought about using add_init_drive() found in device-hotplug.c, > but it is private. Too bad. It looked perfect. > > https://wiki.ubuntu.com/QemuDiskHotplug#Hotplug_USB_Disk > This page say talks about how to do it. This is what it said to do: > > drive_add 0 if=none,id=usbdisk1,file=/tmp/test.img > > Then > > device_add usb-storage,id=usbdisk1,drive=usbdisk1 > > I wasn't able to follow what you said. Do you think you could send me > an example of how you think I should do the mounting of the image > file?
That was the "if that works" part. ;-)
The following works for me:
$ echo foo > bar
$ x86_64-softmmu/qemu-system-x86_64 -qmp stdio -usb -cdrom
~/tmp/archlinux-2015.07.01-dual.iso -enable-kvm -m 512
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2},
"package": ""}, "capabilities": []}}
{'execute': 'qmp_capabilities'}
{"return": {}}
{'execute': 'blockdev-add', 'arguments': {'options': {'id': 'usb-image',
'driver': 'raw', 'file': {'driver': 'file', 'filename': 'bar'}}}}
{"return": {}}
{'execute': 'device_add', 'arguments': {'driver': 'usb-storage', 'id':
'usb-disk', 'drive': 'usb-image'}}
{"return": {}}
In the VM, before device_add:
# cat /dev/sda
cat: /dev/sda: No such file or directory
After device_add:
# cat /dev/sda
foo
Unplugging the device can be done with device_del; but there is no
blockdev-del yet, so the image file will remain lingering.
Max
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