Christoph Hellwig wrote: > On Wed, Feb 03, 2010 at 01:00:47PM -0600, Anthony Liguori wrote: > > But I don't think this is the wrong place to do it. The > > BlockDriverState reflects that backing device, not the emulated device > > itself. In this case, you're trying to set a property of the emulated > > device. > > I think that's very borderline. While the emulated device exposes these > properties, they are in fact a property of the backing storage, the > right sector and min/max I/O sizes are determined by the backing storage > device. > > > I think these need to be qdev properties of the respective devices. > > From a UI perspective, you can still expose -drive options for the end > > user to consume, but this data should be associated with the devices > > themselves. > > In addition to not really beeing more logical this would be a lot more > effort. We'd need to add properties to all the device, which means > including dealing with the n+1 ide variants, the virtio-pci proxy, etc. > > If you believe it really needs to be in the qdev properties I'll > implement it, but I suspect the current version is a better idea.
If you move your VM to a new system with different backing devices, sometimes you want to be sure there is no guest-visible change. Or even if you just replace a drive - you might prefer confidence that the guest sees no change. Even if you just convert between qcow2 and a raw block device, or the other way, you'll sometimes want to be sure it's not guest-visible. -- Jamie
