[virtio-dev] Re: [virtio-comment] Re: [PATCH 10/11] transport-pci: Use driver notification PCI capability

Michael S. Tsirkin
2023-04-12T05:17:12Z

On Wed, Apr 12, 2023 at 05:06:09AM +0000, Parav Pandit wrote:
>
>
> > From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> > open.org> On Behalf Of Michael S. Tsirkin
>
> > > On that occurrence, hypervisor driver forwards the q notification using the q
> > notification region which is defined by struct virtio_pci_notify_cap.
> >
> > What is wrong with forwarding it on the legacy window?
> Legacy window is configuration registers.
> One has sandwitched q notification register in middle of all the config registers.
> Such registers do not start the VQ data path engines.
> 1.x spec has done the right thing to have dedicated notification region which something an actual pci hw can implement.

okay so.. in fact it turns out existing hardware is not
really happy to emulate legacy. it does not really fit that well.
so maybe we should stop propagating the legacy interface to
modern hardware then.
Add the legacy net header size feature and be done with it.

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MST