On Wed, Mar 27, 2013 at 10:37:20AM +1030, Rusty Russell wrote: > "Michael S. Tsirkin" <mst@xxxxxxxxxx> writes: > > On Mon, Mar 25, 2013 at 08:30:28PM +1030, Rusty Russell wrote: > >> Let's go back a level. Do we still need I/O bars at all now? Or can we > >> say "if you want hundreds of vqs, use mem bars"? > >> > >> hpa wanted the option to have either, but do we still want that? > > > > hpa says having both is required for BIOS, not just for speed with KVM. > > OK so the offset must not be applied to the I/O bar as you suggested. Aha. Yes, good idea. As for how large the offsets are, I am guessing we should either just say offset is vqn * X and data is vqn, or give hypervisors full flexibility with 32 bit offset and arbitrary data. 16 bit offsets seem neither here nor there ... Not a strong preference. > Since AFAICT I/O bars are deprecated, should we insist that there be a > memory bar, and the I/O bar is optional? Or just leave it entirely > undefined, and say there can be either or both? I would make the memory bar required and the I/O bar optional. Again not a strong preference. > I dislike the idea of BIOS code which assumed an I/O bar and thus won't > work with a compliant device which doesn't provide one. I'd prefer all > compliant drivers to work with all compliant devices. > > Cheers, > Rusty. In any case, the only thing we would want in the IO BAR is the notification. So we should add a way to control device configuration through PCI configuration. An offset/data pair will do the trick. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
