On Thu, 10 Dec 2020 11:11:17 +0800 Shenming Lu <lushenm...@huawei.com> wrote:
> On 2020/12/9 20:45, Cornelia Huck wrote: > > On Wed, 9 Dec 2020 16:09:18 +0800 > > Shenming Lu <lushenm...@huawei.com> wrote: > > > >> In the VFIO VM state change handler, VFIO devices are transitioned > >> in the _SAVING state, which should keep them from sending interrupts. > >> Then we can save the pending states of all interrupts in the GIC VM > >> state change handler (on ARM). > >> > >> So we have to set the priority of the VFIO VM state change handler > >> explicitly (like virtio devices) to ensure it is called before the > >> GIC's in saving. > > > > What this patch does is to make the priority of the vfio migration > > state change handler depending on the position in the qdev tree. As all > > state change handlers with no explicit priority are added at priority > > 0, this will make sure that this handler runs before (save) resp. after > > (restore) nearly all other handlers, which will address your issue here > > (and possibly similar ones). > > > > So, this patch seems fine for now, but I'm wondering whether we need to > > think more about priorities for handlers in general, and if there are > > more hidden dependencies lurking in there. > > As far as I know, as for the migration of interrupt, on x86 the sync from > the PIR field to the Virtual-APIC page for posted interrupts (in > KVM_GET_LAPIC ioctl) is after the pause of VFIO devices, which is fine. > Not sure about others... Interrupt handling had been my first guess, but it seems most interrupt controllers don't use a state change handler anyway. "handlers in general" actually also referred to use cases outside of vfio migration, so out of scope of this patch... > > Thanks, > Shenming > > > > >> > >> Signed-off-by: Shenming Lu <lushenm...@huawei.com> > >> Reviewed-by: Kirti Wankhede <kwankh...@nvidia.com> > >> --- > >> hw/vfio/migration.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c > >> index 3b9de1353a..97ea82b100 100644 > >> --- a/hw/vfio/migration.c > >> +++ b/hw/vfio/migration.c > >> @@ -862,7 +862,8 @@ static int vfio_migration_init(VFIODevice *vbasedev, > >> register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, > >> &savevm_vfio_handlers, > >> vbasedev); > >> > >> - migration->vm_state = > >> qemu_add_vm_change_state_handler(vfio_vmstate_change, > >> + migration->vm_state = qdev_add_vm_change_state_handler(vbasedev->dev, > >> + > >> vfio_vmstate_change, > >> vbasedev); > >> migration->migration_state.notify = vfio_migration_state_notifier; > >> add_migration_state_change_notifier(&migration->migration_state); > > > > . > > > In any case, Reviewed-by: Cornelia Huck <coh...@redhat.com>
