On Fri, Nov 14, 2025 at 06:48:42AM +0100, Thomas Huth wrote: > On 13/11/2025 20.32, Peter Xu wrote: > > On Thu, Nov 13, 2025 at 12:46:55PM -0500, Michael S. Tsirkin wrote: > > > failing to start a perfectly good qemu which used to work > > > because you changed kernels is better than failing to migrate how? > > > > > > > I agree this is not pretty. > > > > The very original proposal was having extra features to be OFF by default, > > only allow explicit selections to enable them when the mgmt / user is aware > > of the possible hosts to run on top. > > Could it maybe be tied to the "-nodefaults" option of QEMU? If you run QEMU > with "-nodefaults" (which you should do when planning a migration later), > these extra features that depend on the kernel version stay OFF. If you run > QEMU without "-nodefaults", QEMU could enable them if supported by the > kernel. So that would benefit both, the people running QEMU via management > layers (using -nodefaults), and the people who just want to quickly launch > QEMU on the command line. WDYT?
Are the "default set of devices" when without -nodefaults more or less stable (aka, still live migratable)? If so, I wonder if there're still people relying on migrations but using default devices. The other question is, such proposal also means auto-probe will be OFF for all serious users. I am personally OK with such, however it means it'll also reduce the test coverage that Michael was looking for on new network features, when QEMU is running on new kernels. Thanks, -- Peter Xu
