On Mon, Oct 04, 2021 at 04:27:23PM +0200, Cornelia Huck wrote:

On Mon, Oct 04 2021, "Michael S. Tsirkin" [off-list ref] wrote:

quoted

On Mon, Oct 04, 2021 at 02:01:14PM +0200, Cornelia Huck wrote:

quoted

On Sun, Oct 03 2021, "Michael S. Tsirkin" [off-list ref] wrote:

quoted

@@ -160,6 +163,33 @@ \subsection{Legacy Interface: A Note on Feature
 Specification text within these sections generally does not apply
 to non-transitional devices.
 
+\begin{note}
+The device offers different features when used through
+the legacy interface and when operated in accordance with this
+specification.
+\end{note}
+
+Transitional drivers MUST use Devices only through the legacy interface

s/Devices only through the legacy interface/devices through the legacy
interface only/

?

Both versions are actually confused, since how do you
find out that device does not offer VIRTIO_F_VERSION_1?

I think what this should really say is

Transitional drivers MUST NOT accept VIRTIO_F_VERSION_1 through
the legacy interface.

Ok, that makes sense.

Would it make sense that transitional drivers MUST accept VERSION_1
through the non-legacy interface? Or is that redundant?

We already have:

A driver MUST accept VIRTIO_F_VERSION_1 if it is offered.

quoted

Does linux actually satisfy this? Will it accept VIRTIO_F_VERSION_1
through the legacy interface if offered?

I think that the Linux drivers will not operate on feature bit 32+ if
they are in legacy mode?

Well ... with PCI there's no *way* for host to set bit 32 through
legacy. But it might be possible with MMIO/CCW. Can you tell me
what happens then?

quoted

quoted

Generally, looks good to me.

Do we want to also add explanation that features can be
changed until FEATURES_OK?

I always considered that to be implict, as feature negotiation is not
over until we have FEATURES_OK. Not sure whether we need an extra note.

Well Halil here says once you set a feature bit you can't clear it.
So maybe not ...

-- 
MST

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