diff mbox series

[v2,02/15] include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE

Message ID 20220524154056.2896913-3-alex.bennee@linaro.org
State Superseded
Headers show
Series virtio-gpio and various virtio cleanups | expand

Commit Message

Alex Bennée May 24, 2022, 3:40 p.m. UTC
When debugging a new vhost user you may be surprised to see
VHOST_USER_F_PROTOCOL getting squashed in the maze of
backend_features, acked_features and guest_features. Expand the
description here to help the next poor soul trying to work through
this.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 include/hw/virtio/virtio.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Stefan Hajnoczi May 25, 2022, 4:04 p.m. UTC | #1
On Tue, May 24, 2022 at 04:40:43PM +0100, Alex Bennée wrote:
> When debugging a new vhost user you may be surprised to see
> VHOST_USER_F_PROTOCOL getting squashed in the maze of
> backend_features, acked_features and guest_features. Expand the
> description here to help the next poor soul trying to work through
> this.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  include/hw/virtio/virtio.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index db1c0ddf6b..2b2587d324 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -24,7 +24,12 @@
>  #include "qom/object.h"
>  #include "hw/virtio/vhost.h"
>  
> -/* A guest should never accept this.  It implies negotiation is broken. */
> +/*
> + * A guest should never accept this.  It implies negotiation is
> + * broken between the driver frontend and the device. This bit is
> + * re-used for vhost to advertise VHOST_USER_F_PROTOCOL_FEATURES

s/vhost/vhost-user/

> + * between QEMU and a vhost backend.
> + */
>  #define VIRTIO_F_BAD_FEATURE		30
>  
>  #define VIRTIO_LEGACY_FEATURES ((0x1ULL << VIRTIO_F_BAD_FEATURE) | \
> -- 
> 2.30.2
>
diff mbox series

Patch

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index db1c0ddf6b..2b2587d324 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -24,7 +24,12 @@ 
 #include "qom/object.h"
 #include "hw/virtio/vhost.h"
 
-/* A guest should never accept this.  It implies negotiation is broken. */
+/*
+ * A guest should never accept this.  It implies negotiation is
+ * broken between the driver frontend and the device. This bit is
+ * re-used for vhost to advertise VHOST_USER_F_PROTOCOL_FEATURES
+ * between QEMU and a vhost backend.
+ */
 #define VIRTIO_F_BAD_FEATURE		30
 
 #define VIRTIO_LEGACY_FEATURES ((0x1ULL << VIRTIO_F_BAD_FEATURE) | \