Re: [Qemu-devel] [RfC PATCH] virtio-pci: place msix regions in modern virtio bar

[Michael S. Tsirkin]

On Fri, Jan 23, 2015 at 03:48:28PM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> > >  Also seabios wouldn't map the bar
> > > above 4G.
> 
> > We can teach it to do that, and even if not, OS can do it on hotplug.
> 
> Just to clarify: seabios can do it in the general case, it just wouldn't
> do it for xhci specifically because otherwise the seabios xhci driver
> wouldn't be able to reach the registers any more ...
> 
> For non-transitional virtio-{blk,scsi,net} devices seabios (and ipxe)
> would have a simliar problem btw:  When mapping the bars above 4G it
> can't handle the devices any more.

You can always use the config cap for this.
I didn't implement it yet, but I will.

> But we'll probably stick to transitional by default for a while (where
> seabios can just use the legacy registers in io address space),

io *is* very crowded. I think we should try and code up modern drivers
when we have the time.

> and
> there also is ovmf coming which runs in 64bit mode so mapping the bars
> high isn't a problem there.
> 
> cheers,
>   Gerd
>