On Tue, May 19, 2020 at 01:41:08PM -0500, Eric Blake wrote: > On 5/19/20 12:56 PM, Masayoshi Mizuma wrote: > > Hello, > > > > I would like to discard any changes while the qemu guest OS is done. > > I can do that with snapshot and drive option. > > However, snapshot option doesn't work for the device which set by > > blockdev option like as: > > > > $QEMU --enable-kvm \ > > -m 1024 \ > > -nographic \ > > -serial mon:stdio \ > > -blockdev driver=file,node-name=mydisk,filename=/mnt/fedora.qcow2 \ > > -blockdev driver=qcow2,node-name=vda,file=mydisk \ > > -device virtio-blk-pci,drive=vda,bootindex=1 \ > > -snapshot > > > > I would like to use blockdev option to set the device because > > libvirt uses blockdev option for disk element. > > > > If there's no way to do so, does that make sense to get available > > snapshot option to blockdev as well? If that makes sense, I'll try to > > implement that. > > > > As for qcow2, I think we can do such things to use qemu-img snapshot > > command, for example save the original image and restore the image > > after the qemu guest OS is shutdowned. However, it may be complecated > > for user. I would like the simple way like as snapshot/drive option... > > > > If I'm missing something, let me know. > > > > Sounds like a repeat of this thread: > https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg06144.html > > where the consensus is yes, -blockdev and -snapshot are incompatible, > libvirt has plans to use the <transient/> tag to behave the same as what > -snapshot does (but no one has implemented it yet), and in the meantime, it > is possible to force libvirt to avoid -blockdev if you still need to supply > -snapshot behind libvirt's back. Thank you for the info! I didn't notice the thread. I got we should implement that feature for libvirt side, not qemu. Thanks! Masa > > -- > Eric Blake, Principal Software Engineer > Red Hat, Inc. +1-919-301-3226 > Virtualization: qemu.org | libvirt.org >
