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

[Gerd Hoffmann]

  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.

But we'll probably stick to transitional by default for a while (where
seabios can just use the legacy registers in io address space), and
there also is ovmf coming which runs in 64bit mode so mapping the bars
high isn't a problem there.

cheers,
  Gerd