Thread (52 messages) 52 messages, 4 authors, 2021-10-06

Re: [RFC PATCH 1/1] virtio: write back features before verify

From: Cornelia Huck <cohuck@redhat.com>
Date: 2021-10-04 14:27:34
Also in: linux-s390, lkml

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

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?
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.

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