> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Sent: Wednesday, November 23, 2022 7:29 PM > > On Wed, Nov 23 2022 at 07:57, Kevin Tian wrote: > >> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > >> + * One solution is to let the root domain handle the initialization that's > >> + * why there is the @domain and the @msi_parent_domain pointer. > > > > This is the part which I don't quite understand (sorry with limited > knowledge > > in this area). > > > > In concept a hierarchical model has restrictions added up when moving > > down to lower layers i.e. presumably the root domain decides the minimal > > supported capabilities. In this case there is no need of a real parent pointer > > as long as every domain in the stack incrementally adds its restrictions to > > info->flags. > > > > I can see why this is required for x86 given that MULTI_MSI is supported > > only with IR. and we cannot make vector domain inclusively claiming > > MULTI_MSI since it's completely broken when the vector domain becomes > > the parent itself, in absence of IR. > > > > Just be curious whether this intermediate-parent-deciding-restrictions > > is generic instead of x86 specific, e.g. is it possible to have a 4-layers > > hierarchy where the root parent wants to check both two intermediate > > parents? > > Sure. Nothing prevents you from doing so: > > dom4: > .init... = dom4_init > > dom4_init() > do_stuff() > invoke parent init > > dom3: > .init... = parent_init > > dom2: > .init... = dom2_init > > dom2_init() > do_stuff() > invoke parent init > > .... > > See? > yes. with the hierarchy being arch specific those dependencies can be easily figured out.
