On Tue, Jul 19, 2022 at 4:02 PM Laine Stump <laine@xxxxxxxxx> wrote: > > On 7/18/22 11:15 AM, Jiri Denemark wrote: > > On Mon, Jul 18, 2022 at 10:40:56 +0200, Eugenio Perez Martin wrote: > >> On Mon, Jul 18, 2022 at 10:25 AM Jiri Denemark <jdenemar@xxxxxxxxxx> wrote: > >>> Which in ideal case would mean only a QMP command (such as > >>> hotplugging a non-migratable device) is the only way to add migration > >>> blocker. If this is true, than we're safe as libvirt does not allow such > >>> commands between qemuMigrationSrcIsAllowed and migration start. > >>> > >> > >> Ok, that rules out a few bad use cases. I can do a fast lookup to > >> check if blockers can be added without the knowledge of libvirt. > >> > >>> That said, is there a reason for not implementing the correct solution > >>> right away as a separate patch? > >>> > >> > >> I was not sure if libvirt already had another way to check, for > >> example, if the vhost device didn't have VHOST_F_LOG_ALL feature. > > > > I'm not aware of such check, but even if it exists, checking for > > migration blockers looks like the right way of doing things anyway. > > Actually that's been on my todo list for a long time - for any qemu that > supports the QMP command that checks for migratability, we should be > calling this command rather than checking against our own internal list > (which is really just an "informed guess") of what can't be migrated. > This way we'll always get the right answer (or at least what QEMU > believes to be the right answer :-)). Fixing it this way will also mean > that migration of VFIO devices will just "magically" start working once > a migration-supporting driver is written for the device, and the correct > vfio driver is bound to the device (this latter item is also on my list). > > So if you're up for making the patch to call the QMP command, I'd be > happy to review it! > Thanks! Actually I'd need some guidance first, I'm not very used to libvirt code. As I understand I should create a function in qemu_agent.h/c, a getter similar to qemuAgentGetFSInfo. How can I get a qemuAgent from qemuMigrationSrcIsAllowed? I only have a virQEMUDriver there. For now it should be enough to delete vdpa hardcoded negation, and then other parts of libvirt can delete other hardcoded checks, isn't it? Thanks!
