On Wed, Mar 27, 2013 at 10:37:20AM +1030, Rusty Russell wrote:

"Michael S. Tsirkin" [off-list ref] writes:

quoted

On Mon, Mar 25, 2013 at 08:30:28PM +1030, Rusty Russell wrote:

quoted

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