pc,virtio: features, tests, fixes, cleanups

[PULL 02/55] include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE

Michael S. Tsirkin posted 55 patches 3 years, 2 months ago

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Maintainers: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Igor Mammedov <imammedo@redhat.com>, Ani Sinha <ani@anisinha.ca>, Peter Maydell <peter.maydell@linaro.org>, Shannon Zhao <shannon.zhaosl@gmail.com>, Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>, Raphael Norwitz <raphael.norwitz@nutanix.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Peter Xu <peterx@redhat.com>, Jason Wang <jasowang@redhat.com>, Ben Widawsky <ben.widawsky@intel.com>, Jonathan Cameron <jonathan.cameron@huawei.com>, Fam Zheng <fam@euphon.net>, "Alex Bennée" <alex.bennee@linaro.org>, Viresh Kumar <viresh.kumar@linaro.org>, Mathieu Poirier <mathieu.poirier@linaro.org>, Markus Armbruster <armbru@redhat.com>, Michael Roth <michael.roth@amd.com>, Eric Blake <eblake@redhat.com>, Thomas Huth <thuth@redhat.com>, Laurent Vivier <lvivier@redhat.com>

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[PULL 02/55] include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE

Posted by Michael S. Tsirkin 3 years, 2 months ago

From: Alex Bennée <alex.bennee@linaro.org>

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>

Message-Id: <20220802095010.3330793-6-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 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..9bb2485415 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-user to advertise VHOST_USER_F_PROTOCOL_FEATURES between QEMU
+ * and a vhost-user backend.
+ */
 #define VIRTIO_F_BAD_FEATURE		30
 
 #define VIRTIO_LEGACY_FEATURES ((0x1ULL << VIRTIO_F_BAD_FEATURE) | \
-- 
MST