RE: [patch V2 12/33] PCI/MSI: Add support for per device MSI[X] domains

[Tian, Kevin]

> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Sent: Thursday, November 24, 2022 5:50 AM
> 
> >> This is general PCI MSI logic. So an open related to my rely to patch02,
> >> is it correct for PCI core to assume that the real parent imposes all the
> >> restrictions and there is no need to further go down the hierarchy?
> >
> > That was my working assumption and it turned out to be correct with both
> > x86 and ARM.
> 
> As a follow up, I went through some of the other architectures,
> especially the places which have extra limitations and it turns out that
> the restriction comes always from the direct parent.
> 
> If that ever changes then we need a callback which lets us evaluate the
> resulting capabilities through the hierarchy. That's nothing which can
> be evaluated directly.
> 
> Just look at the x86 hierarchy with IR. IR allows multi PCI-MSI, but the
> vector domain does not. Who is right? That's a decision which is made in
> the particular hierarchy.

make sense.

> 
> For now it's valid that the direct MSI parent has the proper set
> available.
> 

probably above can be marked out in the comment.