On Wed, 2011-11-09 at 23:14 +0200, Michael S. Tsirkin wrote:> On Wed, Nov 09, 2011 at 10:57:28PM +0200, Sasha Levin wrote:> > On Wed, 2011-11-09 at 22:52 +0200, Michael S. Tsirkin wrote:> > > On Wed, Nov 09, 2011 at 10:24:47PM +0200, Sasha Levin wrote:> > > > On Wed, 2011-11-09 at 21:59 +0200, Michael S. Tsirkin wrote:> > > > > > > > [snip]> > > > > > > > > +\begin_layout Enumerate> > > > > +Reset the device.> > > > > + This is not required on initial start up.> > > > > +\end_layout> > > > > +> > > > > +\begin_layout Enumerate> > > > > +The ACKNOWLEDGE status bit is set: we have noticed the device.> > > > > +\end_layout> > > > > +> > > > > +\begin_layout Enumerate> > > > > +The DRIVER status bit is set: we know how to drive the device.> > > > > +\end_layout> > > > > +> > > > > +\begin_layout Enumerate> > > > > +> > > > > +\change_inserted 1986246365 1320838089> > > > > +PCI capability list scan, detecting virtio configuration layout using Virtio> > > > > + Structure PCI capabilities.> > > > > > > > Does the legacy space always gets mapped from BAR0?> > > > > > > > If yes,> > > > > > Yes and this is repeated in several places. Not clear? How can this> > > be made clearer?> > > > Do you mean comments such as "For backwards compatibility, devices> > should also present legacy configuration space in the first I/O region> > of the PCI device"? What I understood from it is that the device should> > have a legacy config in case it's used with an older guest, but I didn't> > understand from it that the legacy config will be used even if new> > layout is present.> > Yes, this is what I meant. New guest is required to use the new space> and not the legacy one. So you dont need a legacy space for the at all.> But practically, we'll need to support old guests for a long while.> > > > > It'll be a bit harder deprecating it in the future.> > > > > > Harder than ... what ?> > > > Harder than allowing devices not to present it at all if new layout> > config is used.> > Yes, it's allowed if you know you have a new guest. It says> explicitly that drivers are required to use new capabilities> is they are there.> > > Right now the simple implementation is to use MMIO for> > config and device specific, and let it fallback to legacy for ISR and> > notifications (and therefore, this is probably how everybody will> > implement it), which means that when you do want to deprecate legacy,> > there will be extra work to be done then, instead of doing it now.> > If hypervisors don't implement the new layout then drivers will> have to keep supporting the old one. I don't think we can do> much about that.> > > > IMO there's no way to put legacy anywhere except the first BAR> > > without breaking existing guests.> > > > It's not about where we put legacy, it's about how easy it is to drop> > legacy entirely.> > We can only do this after all guests and hypervisors are updated. When> they are, we can drop legacy from drivers and hypervisors, and> I don't see a way to make it easier.Well, in that case, why does the PCI cap probing is #4 in the deviceinit list? Shouldn't we getting the layout and mapping it before wewrite to the status byte?-- Sasha.