On Mon, Jan 25, 2021 at 10:57:14AM +0000, Parav Pandit wrote: > Hi Edwin, > > > From: Edwin Peer <edwin.peer@xxxxxxxxxxxx> > > Sent: Monday, January 25, 2021 2:17 AM > > > > On Fri, Jan 22, 2021 at 11:37 AM Saeed Mahameed <saeed@xxxxxxxxxx> > > wrote: > > > > > For more detailed information about subfunctions please see detailed tag > > > log below. > > > > Apologies for the tardy question out of left field, but I've been > > thinking about this some more. If I recall, the primary motivation for > > this was a means to effectively address more VFs? But, why can't the > > device simply expose more bus numbers? > > Several weeks back, Jason already answered this VF scaling question > from you at discussion [1]. To add a little more colour, the PCI spec design requires a CAM (ie search) to figure out which function an incoming address is connected to because there are no restrictions on how BAR's of each function have to be layed out. SRIOV and SF's require a simple linear lookup to learn the "function" because the BAR space is required to be linear. Scaling a CAM to high sizes is physicaly infeasible, so all approaches to scaling PCI functions go this road of having a single large BAR space. Jason
