On Wed, 2011-11-30 at 10:10 +1030, Rusty Russell wrote:

On Mon, 28 Nov 2011 11:15:31 +0200, Sasha Levin [off-list ref] wrote:

quoted

On Mon, 2011-11-28 at 11:25 +1030, Rusty Russell wrote:

quoted

I'd like to see kvmtools remove support for legacy mode altogether,
but they probably have existing users.

While we can't simply remove it right away, instead of mixing our
implementation for both legacy and new spec in the same code we can
split the virtio-pci implementation into two:

	- virtio/virtio-pci-legacy.c
	- virtio/virtio-pci.c

At that point we can #ifdef the entire virtio-pci-legacy.c for now and
remove it at the same time legacy virtio-pci is removed from the kernel.

Hmm, that might be neat, but we can't tell the driver core to try
virtio-pci before virtio-pci-legacy, so we need detection code in both
modules (and add a "force" flag to virtio-pci-legacy to tell it to
accept the device even if it's not a legacy-only one).

I was thinking more in the direction of fallback code in virtio-pci.c to
virtio-pci-legacy.c.

Something like:
#ifdef VIRTIO_PCI_LEGACY
[Create BAR0 and map it to virtio-pci-legacy.c]
#endif

So BAR0 isn't defined as long as legacy code is there, which makes
falling back to legacy pretty simple.

-- 

Sasha.