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From: "Alex Bennée" <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Cc: slp@redhat.com, mst@redhat.com, marcandre.lureau@redhat.com,
	stefanha@redhat.com, mathieu.poirier@linaro.org,
	viresh.kumar@linaro.org, "Alex Bennée" <alex.bennee@linaro.org>
Subject: [PATCH v2 02/15] include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE
Date: Tue, 24 May 2022 16:40:43 +0100	[thread overview]
Message-ID: <20220524154056.2896913-3-alex.bennee@linaro.org> (raw)
In-Reply-To: <20220524154056.2896913-1-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>
---
 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
+ * between QEMU and a vhost backend.
+ */
 #define VIRTIO_F_BAD_FEATURE		30
 
 #define VIRTIO_LEGACY_FEATURES ((0x1ULL << VIRTIO_F_BAD_FEATURE) | \
-- 
2.30.2



  parent reply	other threads:[~2022-05-24 15:43 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-24 15:40 [PATCH v2 00/15] virtio-gpio and various virtio cleanups Alex Bennée
2022-05-24 15:40 ` [PATCH v2 01/15] contrib/vhost-user-blk: fix 32 bit build and enable Alex Bennée
2022-05-25 16:03   ` Stefan Hajnoczi
2022-05-31  4:29   ` Raphael Norwitz
2022-05-24 15:40 ` Alex Bennée [this message]
2022-05-25 16:04   ` [PATCH v2 02/15] include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE Stefan Hajnoczi
2022-05-24 15:40 ` [PATCH v2 03/15] include/hw/virtio: document vhost_get_features Alex Bennée
2022-05-25 16:06   ` Stefan Hajnoczi
2022-05-24 15:40 ` [PATCH v2 04/15] include/hw/virtio: document vhost_ack_features Alex Bennée
2022-05-25 16:11   ` Stefan Hajnoczi
2022-05-24 15:40 ` [PATCH v2 05/15] hw/virtio: add boilerplate for vhost-user-gpio device Alex Bennée
2022-06-10  8:37   ` Vincent Whitchurch
2022-07-06 13:37     ` Alex Bennée
2022-05-24 15:40 ` [PATCH v2 06/15] hw/virtio: add vhost-user-gpio-pci boilerplate Alex Bennée
2022-05-24 15:40 ` [PATCH v2 07/15] tests/qtest: pass stdout/stderr down to subtests Alex Bennée
2022-05-24 15:43   ` Thomas Huth
2022-05-24 15:40 ` [PATCH v2 08/15] tests/qtest: add a timeout for subprocess_run_one_test Alex Bennée
2022-05-24 15:46   ` Thomas Huth
2022-05-24 15:40 ` [PATCH v2 09/15] tests/qtest: use qos_printf instead of g_test_message Alex Bennée
2022-05-24 15:40 ` [PATCH v2 10/15] tests/qtest: catch unhandled vhost-user messages Alex Bennée
2022-05-24 15:40 ` [PATCH v2 11/15] tests/qtest: use g_autofree for test_server_create_chr Alex Bennée
2022-05-24 15:40 ` [PATCH v2 12/15] tests/qtest: plain g_assert for VHOST_USER_F_PROTOCOL_FEATURES Alex Bennée
2022-06-02 16:26   ` Thomas Huth
2022-05-24 15:40 ` [PATCH v2 13/15] tests/qtest: implement stub for VHOST_USER_GET_CONFIG Alex Bennée
2022-05-24 15:40 ` [PATCH v2 14/15] tests/qtest: add a get_features op to vhost-user-test Alex Bennée
2022-05-24 15:40 ` [PATCH v2 15/15] tests/qtest: enable tests for virtio-gpio Alex Bennée
2022-05-25 16:17   ` Stefan Hajnoczi
2022-05-25 22:35     ` Alex Bennée
2022-05-26  8:06       ` Stefan Hajnoczi
2022-05-25 16:14 ` [PATCH v2 00/15] virtio-gpio and various virtio cleanups Stefan Hajnoczi
2022-07-07 13:38   ` Alex Bennée
2022-07-07 14:03     ` Stefan Hajnoczi
2022-07-07 15:20       ` Alex Bennée
2022-07-07 16:43         ` Stefan Hajnoczi

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