[ipxe-devel] [ipxe/ipxe] virtio changes 5/2016 (#55)

[Gerd Hoffmann]

On Mo, 2016-06-20 at 15:44 +0100, Michael Brown wrote:
> On 20/06/16 15:37, Ladi Prosek wrote:
> > Thanks - virtio devices may be configured to expose both I/O and memory
> > BARs, with either type being enough to drive the device. It is basically
> > a back-compat setup where older drivers can still use I/O ports and
> > newer may choose to use the so called "modern" interface.
> >
> > We would like to avoid enabling PCI_COMMAND_IO / PCI_COMMAND_MEM if the
> > driver is not going to use it.
> 
> Why?

It is nice to have.  It will make sure the driver will only use the
interface it intends to use and doesn't mix IO-based legacy device
access and MMIO-based modern device access by accident.

> What goes wrong if iPXE just enables both?

Nothing (in theory).

cheers,
  Gerd