> From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Sent: Tuesday, February 14, 2023 7:00 PM
>
> On Fri, Feb 10, 2023 at 02:11:23AM +0000, Tian, Kevin wrote:
>
> > My confusion is that we have different flows between detach/attach
> > and replace.
> >
> > today with separate detach+attach we have following flow:
> >
> > Remove device from current hwpt;
> > if (last_device in hwpt) {
> > Remove hwpt domain from current iopt;
> > if (last_device in group)
> > detach group from hwpt domain;
> > }
> >
> > if (first device in group) {
> > attach group to new hwpt domain;
> > if (first_device in hwpt)
> > Add hwpt domain to new iopt;
> > Add device to new hwpt;
> >
> > but replace flow is different on the detach part:
> >
> > if (first device in group) {
> > replace group's domain from current hwpt to new hwpt;
> > if (first_device in hwpt)
> > Add hwpt domain to new iopt;
> > }
> >
> > Remove device from old hwpt;
> > if (last_device in old hwpt)
> > Remove hwpt domain from old iopt;
> >
> > Add device to new hwpt;
> >
> > I'm yet to figure out whether we have sufficient lock protection to
> > prevent other paths from using old iopt/hwpt to find the device
> > which is already attached to a different domain.
>
> With Jason's new series, the detach() routine is lighter now.
>
> I wonder if it'd be safer now to do the detach() call after
> iommu_group_replace_domain()?
>
yes, looks so.
